THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 508 478-9200; Fax +1 508 478-0990; Web: www.thatcorp.com
Copyright © 2016, THAT Corporation; Doc 600173 Rev 03
Low-Noise, Differential
Audio Preamplifier IC
THAT1583
FEATURES
• Low Noise:
-128.9dBu (1.9nV/√Hz) EIN@60dB gain
• Low THD+N:
0.001% ≤ 40 dB gain
0.006% @ 60 dB gain
• Low Current: 7.0 mA typ
• Wide Bandwidth: 1.7MHz @40dB gain
• High Slew Rate: 50 V/µs
• Wide Output Signal Swing: > +28dBu
• Gain adjustable from 0 to >60 dB
• Differential output
• Small 4 x 4mm QFN16 package
• Mates with THAT's family of Digital
Preamplifier Controller ICs
APPLICATIONS
• Microphone Preamplifiers
• Digitally-Controlled Microphone
Preamplifiers
• Differential Low-Noise Preamplifiers
• Differential Summing Amplifiers
• Differential Variable-Gain Amplifiers
• Moving-Coil Transducer Amplifiers
• Line Input Stages
• Audio
• Sonar
• Instrumentation
Description
The THAT 1583 is a
versatile, high performance
current-feedback amplifier suitable for differential
microphone preamplifier and bus summing
applications. It improves on previous, traditional
current-feedback designs (viz. THAT's 1510 &
1512) by offering a more versatile configuration
that can yield lower noise at low gains, lower
distortion overall, and higher slew rate.
Amplifier gain is determined by three external
resistors (R
A
, R
B
, and R
G
). This makes it possible to
optimize noise and bandwidth over a wide range of
gains, as well as optimize the taper of gain vs.
rotation in variable-gain, pot-controlled applications.
The 1583's differential output simplifies connec-
tions to differential input devices such as A/D
converters.
When required,
designers are free to
optimiz
e the output differential amplifier to suit
the specific application.
In analog variable-gain applications the part
supports the traditional approach using fixed R
A
and R
B
and a single-section variable element for
R
G
. But, it also supports a dual-element alternative
that offers improved performance.
In addition to analog-controlled applications, the
1583 is designed to mate perfectly with THAT's
series of Digital Preamplifier Controller ICs to
produce an optimized, digitally controlled
preamplifier.
The 1583 operates from as little as ±5 V up
through ±18 V supplies. It accepts greater than
+28 dBu input signals at unity gain when
operated from ±18V supplies.
Figure 1. THAT1583 Block Diagram
Pin Name
QFN Pin
N/C* 1
OUT2 2
OUT1 3
N/C* 4
N/C* 5
Rg1 6
IN1 7
N/C* 8
N/C* 9
IN2 10
N/C* 11
V- 12
V+ 13
N/C* 14
Rg2 15
N/C* 16
V- Thermal Pad
Table 1. Pin Assignments
* N/C pins should be left open and not connected to other traces on the PCB
THAT 1583 Low-Noise Page 2 of 16 Document 600173 Rev 03
Differential Audio Preamplifier IC
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 508 478-9200; Fax +1 508 478-0990; Web: www.thatcorp.com
Copyright © 2016, THAT Corporation; All rights reserved.
SPECIFICATIONS
1
Absolute Maximum Ratings
2
Supply Voltage (V+) - (V-)
40 V
Operating Temperature Range (T
OP
) -40 to +85 ºC
Maximum Input Voltage (V
IMax
) (V+) +0.5V to (V-)-
0.5V
Junction Temperature (T
JMAX
) +125 ºC
Storage Temperature Range (T
STG
) -
40 to +125 ºC
Output Short-Circuit Duration,
between outputs and/or GND (t
SH
) Continuous
Electrical Characteristics
3 , 4 , 5
Parameter Symbol Conditions Min Typ Max Units
Power Supply
Supply Voltage V+; - (V-) Referenced to GND 5 — 18 V
Supply Current I+; -(I-) No Signal — 7.0 10 mA
Input Characteristics
Input Bias Current I
B
No signal; either input connected to GND — 2.0 4.4 µA
Input Offset Current I
B-OFF
No signal -440 — +440 nA
R
G
Input Bias Current I
BRG
No signal -20 +2 +20 µA
R
G
Input Offset Current I
BRG-OFF
No signal -4.5 — +4.5 µA
Differential Input Offset Voltage V
OS
No signal, Includes I
BRG-OFF
* R
G
0 dB gain -15 — +15 mV
+60 dB gain -450 — +450 µV
Input Common Mode Voltage Range V
IN_CM
Common Mode (V-) + 1.5 — (V+) -4 V
Maximum Differential Input Level V
IN-BAL
R
G
= ∞ — 26.4 — dBu
Supply Voltage ±18V — 28.0 — dBu
Output Characteristics
Differential Output Offset G = gain -(15 + 0.45*G) — (15 + 0.45*G) mV
Common Mode Output Voltage V
OSCM
No signal; — -630 — mV
IN1, IN2 connected to GND
Maximum Single Output Voltage V
OUT-SINGLE
G=20dB, R
L
= 2 kΩ (V-) + 1.2 — (V+) - 2 V
Differential Short Circuit Current I
SC
R
L
= 0 Ω — ± 70 — mA
Maximum Capacitive Load C
L MAX
Over entire temperature range — — 30 pF
Stable operation 30% overshoot — 75 — pF
Maximum Differential Output Level V
OUT
R
L
= 2 kΩ 28 — — dBu
Gain > 2 dB
1. All specifications are subject to change without notice.
2. Stresses above those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only; the functional operation of
the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.
3. Unless otherwise noted, T
A
= 25ºC, V+ = +15V, V- = -15V.
4. 0 dBu = 0.775 Vrms
5. Unless otherwise noted, feedback resistors = 2.21 kΩ; C
L
= 10 pF. Circuit is as shown in Figure 15.
THAT 1583 Low-Noise Page 3 of 16 Document 600173 Rev 03
Differential Audio Preamplifier IC
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 508 478-9200; Fax +1 508 478-0990; Web: www.thatcorp.com
Copyright © 2016, THAT Corporation; All rights reserved.
Figure 2. Equivalent Input Noise vs Gain and
Source Impedance; BW: 22Hz to 22kHz
Electrical Characteristics (con’t)
3 , 4 , 5
Parameter Symbol Conditions Min. Typ. Max Units
AC Characteristics
Feedback Impedance R
A
= R
B
Refer to Figure 15 2 — — kΩ
Differential Gain A
V
Programmed by R
A
, R
B
, R
G
0 — 70 dB
Refer to Figure 15
Power Supply Rejection Ratio PSRR V+ = -(V-); ±5V to ±18V
0 dB gain — 105 — dB
20 dB gain — 116 — dB
40 dB gain — 140 — dB
60 dB gain — 140 — dB
Bandwidth -3dB f
-3dB
Small signal; R
A
=R
B
=2.21kΩ; Refer to Figure 5
0 dB gain — 14 — MHz
20 dB gain — 9 — MHz
40 dB gain — 1.7 — MHz
60 dB gain — 192 — kHz
Small signal; R
G
=∞ (0 dB gain)
R
A
= R
B
= 2 kΩ — 16 — MHz
R
A
= R
B
= 5 kΩ — 4 — MHz
R
A
= R
B
= 10 kΩ — 1.6 — MHz
Slew Rate SR V
OUT
= 10V
P-P
; R
L
=2kΩ
C
L
=30pF; G=20dB — 50 — V/µs
Total Harmonic Distortion + Noise THD + N V
OUT
= 5V
RMS
; R
L
=2kΩ; f=1kHz; BW=22kHz
0 dB gain — 0.0006 — %
20 dB gain — 0.0008 — %
40 dB gain — 0.001 — %
60 dB gain — 0.006 — %
Equivalent Input Noise Voltage
e
N
Inputs connected to GND; f=1kHz
R
A
= R
B
= 2.21kΩ; Refer to Figure 15
0 dB gain — 40 — nV/√Hz
20 dB gain — 5.7 — nV/√Hz
40 dB gain — 2.3 — nV/√Hz
60 dB gain — 1.9 — nV/√Hz
BW = 22kHz
60 dB gain — -128.9 — dBu
A - weighted ; BW = 22kHz
60 dB gain — -131.2 — dBu
Inputs connected to 150Ω; BW = 22kHz
60 dB gain — -126.5 — dBu
Inputs connected to 150Ω; A - weighted
60 dB gain — -129.3 — dBu
Equivalent Input Noise Current i
N
f = 1kHz; 60 dB gain — 0.8 — pA/√Hz
Noise Figure NF 60 dB gain; Source impedance = 150 Ω — 3.9 — dB
Figure 3. Equivalent Input Noise vs Gain and Bandwidth,
Source Impedance 150Ω
-130
-125
-120
-115
-110
-105
-100
[dBu]
[dB]
0 10 20 30 40 50 60
BW: 22Hz - 22kHz
BW: A-weighted
-130
-125
-120
-115
-110
-105
-100
[dBu]
[dB]
0 10 20 30 40 50 60
R
S
= 150
THAT 1583 Low-Noise Page 4 of 16 Document 600173 Rev 03
Differential Audio Preamplifier IC
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 508 478-9200; Fax +1 508 478-0990; Web: www.thatcorp.com
Copyright © 2016, THAT Corporation; All rights reserved.
Figure 4. Equivalent Input Noise vs Gain and
Feedback Impedance; BW: 22Hz to 22kHz
Figure 6. THD+ Noise vs Level
Figure 5. Bandwidth vs Gain and Feedback Impedance
Figure 7. THD + Noise vs Frequency; Vout = 27dBu,
RL = 10kΩ
Figure 8. Power Supply Rejection vs Frequency
Figure 9. Maximum Output Voltage vs Output Current
-130
-125
-120
-115
-110
-105
-100
-95
-90
[dBu]
[dB]
0 10 20 30 40 50 60
R
A
=R
B
=2k21
R
A
=R
B
=5k
R
A
=R
B
=10k
0.1
1
10
[MHz]
[dB]
0 10 20 30 40 50 60
0.0001
0.001
0.01
0.1
[%]
[dBu]
0 5 10 15 20 25 30
0dB
10dB
20dB
30dB
40dB
50dB
60dB
0.0001
0.001
0.01
0.1
[%]
[Hz]
100 1k 10k 20k
10dB 20dB
30dB
40dB
50dB
60dB
0 dB
40 dB
0
20
40
60
80
100
120
140
[dB]
[Hz]
20 200 2k 20k 200k
-15
-10
-5
0
5
10
15
[V]
[mA]
0 10 20 30 40 50 60 70
V
OUT
P
V
OUT
N
THAT 1583 Low-Noise Page 5 of 16 Document 600173 Rev 03
Differential Audio Preamplifier IC
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 508 478-9200; Fax +1 508 478-0990; Web: www.thatcorp.com
Copyright © 2016, THAT Corporation; All rights reserved.
Figure 13. Representative R
G
Input Bias
Current Distribution
Figure 12. Representative Input Offset Voltage
Distribution, 60dB Gain
Figure 14. Representative R
G
Input Offset
Current Distribution
Figure 10. Maximum Output Level vs. Supply Voltage
Figure 11. Representative Output Offset Voltage
Distribution, 0dB Gain
-600 -400-800 -200 0 200 400 600 800
[uV]
-15 -10-20 -5 0 5 10 15 20
[mV]
-15 -10-20-25-30 -5 0 5 10 15 20 25 30
[uA]
-3 -2-4-5 -1 0 1 2 3 4 5
[uA]
THAT 1583 Low-Noise Page 6 of 16 Document 600173 Rev 03
Differential Audio Preamplifier IC
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 508 478-9200; Fax +1 508 478-0990; Web: www.thatcorp.com
Copyright © 2016, THAT Corporation; All rights reserved.
Amplifier Overview
Referring to Figure 15, the THAT1583's differential
voltage gain (G) is set by the feedback resistors (R
A
and R
B
) and R
G
, as shown in the following equation.
The amplifier's minimum gain is unity (0 dB), which
occurs with infinite R
G
. The feedback resistors
should nominally be equal, though tight tolerance
matching is not required.
= 1 +
+
In low-noise current-feedback amplifiers like the
1583, many performance characteristics depend
critically on the impedance of the feedback network
(R
A
, R
B
, and R
G
).
The 1583 (and 1570) offers a novel approach to an
integrated microphone preamplifier in that all three
gain resistors are external. This gives the designer
freedom to select the optimal values for the best
noise performance at the desired gain setting(s).
Noise versus Gain
The noise performance of a preamplifier based on
the 1583 is determined as the sum of several noise
sources. These are as follows (refer to Figure 15 for
component reference designators):
1. the amplifier's own input voltage noise;
2. the voltage noise of the gain-setting resistor
network (R
G
in parallel with R
A
and R
B
);
3. the voltage noise of the external source im-
pedance, connected to the 1583's input (R
M
in
parallel with R
1
+ R
2
):,
4. the current noise from IN+ and IN-, developed
across the source impedance (R
M
in parallel
with R
1
+R
2
), and
5. the current noise from R
G1
and R
G2
, translated
to a voltage when drawn across the equivalent
impedance of the external gain-setting resistor
network (R
G
in parallel with R
A
and R
B
).
Since all these sources are uncorrelated, mostly
random (Gaussian) noise, these sources all add in
root-mean-square fashion. But which one is most
important changes with gain, so predicting how noise
varies can be complex.
A complete discussion of these sources and their
interaction is beyond the scope of this data sheet.
For more information, see "De-Integrating Integrated
Circuit Preamps", available from THAT Corporation's
web site, especially pages 13 through 20 However,
the following discussion covers the highlights.
At high gains (above 40 dB or so), the system noise
is typically dominated by the first three factors in the
above list. At high gains, for practical values of R
A
,
R
B
, and R
G
(where R
G
is typically less 100Ω) and
typical external source impedances (microphones are
generally around 150Ω), the amplifier's input voltage
noise will be the largest contributor. However, at
1.9 nV/√Hz (-128.9 dBu unweighted, 22 kHz
bandwidth) the amplifier's own input noise is only
1.5 dB higher than that of a 150 Ω microphone (-
130.4 dBu). So, the external source impedance R
M
is
a significant contributor to the total noise of the
system.
At low gains (under about 20 dB), the dominant
noise sources are factors 2 and 5. An important case
occurs at 0 dB (unity) differential gain. In order to
reach 0 dB gain, R
G
is open (infinite resistance). In
this case, the current noise in R
G1
and R
G2
is drawn
across the highest possible impedance (R
A
and R
B
alone, without any shunting effect of R
G
). The only
way to mitigate this noise is to use lower values for
R
A
and R
B
.
Of course, there is a continuum of relative impor-
tances here as gain goes from minimum (0 dB) to
maximum (over 70 dB). As gain varies, the im-
portance of each factor will vary in its own way, each
contributing a different relative amount to the total.
In general, to minimize low-gain noise, we suggest to
keep R
A
and R
B
as small as possible.
Another perspective on noise performance is gained
by measuring the noise using an A-weighting filter.
Figure 3 compares equivalent input noise for various
gains in a 22 kHz bandwidth vs. using an A-weighting
filter. The A-weighting filter improves input noise
performance by about 3 dB.
Bandwidth
An important characteristic of current-feedback
amplifiers is that the amplifier bandwidth is inversely
proportional to the feedback resistance R
A
and R
B
.
The bandwidth decreases with increasing feedback
resistance. As mentioned before, the minimum value
of R
A
and R
B
is determined by the amplifier's stability
and cannot be under any condition lower than 2 kΩ.
Figure 5 shows typical bandwidth versus gain for a
few selected values of feedback resistance.
Theory of Operation
Figure 15. Simple THAT1583 Amplifier Circuit
R
A
R
B
R
G
R
M
R
1
R
2
IN1 OUT+
OUT-
OUT1
OUT2
R
G
1
R
G
2
IN2
THAT 1583 Low-Noise Page 7 of 16 Document 600173 Rev 03
Differential Audio Preamplifier IC
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 508 478-9200; Fax +1 508 478-0990; Web: www.thatcorp.com
Copyright © 2016, THAT Corporation; All rights reserved.
Note that the widest bandwidth may not always be
the optimum condition. In digitally controlled
applications using CMOS switches to vary gain, high
bandwidth may allow charge injected by the switches
to be amplified and sharp voltage spikes to appear at
the output. Lower bandwidth can reduce this effect.
Common Mode Gain
The amplifier common-mode gain is always unity
(0 dB), regardless of the differential gain. So, any
common-mode input signal, along with the amplifi-
er's own common-mode dc offset, will be transferred
faithfully without gain or attenuation to the output.
The common-mode rejection ratio (CMRR) of the part
will equal the differential gain, since differential
signals are amplified while common-mode signals are
not.
The largest impact of significant common-mode
signals is to limit 1583's dynamic range, since they
can cause premature clipping of the input and
outputs. The same will be true for subsequent stages.
The 1583 output has a typical dc common mode
offset of about -600 mV. This constrains output
headroom on negative signal peaks by 600 mV. At
high power supplies, the 600 mV reduction of output
swing may not matter. However, it has a more
significant effect at the minimum power supply. If
desired, a common-mode servo amplifier can be
added to drive the outputs' common-mode voltage to
0 V by lifting the inputs' bias to approximately
+600 mV. Note that it is more important to adjust
the output to zero bias than the input, because the
1583's input voltage range is typically less than that
for its output.
Limiting Differential dc Gain
In the circuit of Figure 15, the amplifier's differen-
tial gain (G) extends to dc. As a result, the differential
dc offset at the outputs will vary with gain. This can
produce audible "thumps" when gain is varied
quickly, and can produce significant and undesirable
output dc offset at maximum gain. Any such offset
will reduce the output voltage swing.
To see how important this is, suppose a particular
1583 has an input offset of 400 µV and an output
offset of 10 mV. The output offset of that part would
be 10.4 mV at unity (0 dB) gain. But, at 60 dB gain,
the output dc offset will be 410 mV. If the gain is
varied quickly, this ~400 mV dc shift will be audible.
This issue can be addressed by ac coupling R
G
as
shown in Figure 16 with capacitor C
G
. The capacitor
forces dc gain to unity regardless of the amplifier
differential gain. This means the output's differential
dc offset will not vary with gain. In the example
above, adding C
G
will set the output dc offset at
10.4 mV regardless of the differential gain.
Note that the R
G
-C
G
network forms a high-pass
filter. The high-pass filter's -3 dB corner frequency is
determined by the following equation.
=
1
2
Note that the cutoff varies with R
G
and therefore
with gain. It is highest with lowest R
G
(which occurs
at the highest gain). This can be a desirable effect in
that at high gains it can significantly reduce the low
frequency rumble and noise from wind or micro-
phone handling.
Consider the circuits shown in Figure 17, which
has a fixed and variable R
G
(R
GF
and R
GV
). At
maximum gain (60 dB), R
G
= 10 Ω. With
C
G
= 3,300 µF, the high-pass corner frequency is
approximately 5 Hz. But, at minimum gain (6 dB),
R
G
= 10kΩ. This drives the cutoff down to 0.005 Hz.
It may well be acceptable to reduce C
G
by a factor of
10, to 330 µF. In this case the high-pass corner
would vary from 50 Hz at 60 dB gain to 0.05 Hz at
6 dB gain.
The dc voltage appearing across C
G
is very small,
less than 450 mV, though its polarity will vary from
sample to sample. C
G
is usually a low voltage
electrolytic type; 6.3 V is generally sufficient. Since
polarized electrolytic capacitors normally can
withstand some small reverse bias, C
G
can be a
polarized capacitor
Figure 16. Simple THAT1583 Circuit with C
G
R
A
R
B
R
G
C
G
R
M
R
1
R
2
IN1 OUT+
OUT-
OUT1
OUT2
R
G
1
R
G
2
IN2
THAT 1583 Low-Noise Page 8 of 16 Document 600173 Rev 03
Differential Audio Preamplifier IC
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 508 478-9200; Fax +1 508 478-0990; Web: www.thatcorp.com
Copyright © 2016, THAT Corporation; All rights reserved.
Analog Gain Control
Traditional integrated microphone preamplifiers
include the feedback resistors (e.g., the THAT1510
and THAT1512) and allow gain to be varied using an
external single-element potentiometer. The 1583
supports a similar configuration in that the designer
may select fixed feedback resistors (R
A
and R
B
). and
vary R
G
as shown in Figure 17. This circuit provides
a maximum gain of 60 dB (when R
G
= 10Ω because
R
GV
= 0 Ω) and a minimum gain of 6 dB (when
R
G
= 10,010 Ω because R
GV
= 10 kΩ).
Refer to Figure 4 for typical noise versus gain with
5 kΩ feedback resistors (R
A
and R
B
). Other minimum
and maximum gains, and noise versus gain perfor-
mance, can be accommodated by selecting different
values of R
A
, R
B
, R
GV
and R
GF
. Typically, reverse log
(audio) taper elements offer the desired behavior in
gain versus rotation wherein gain increases with
clockwise rotation.
An interesting and novel technique permitted by the
1583's "deconstructed" topology is to vary all three
resistors simultaneously, as shown in Figure 18.
Here, we use a dual-element potentiometer as the
gain control. High gain occurs by decreasing R
G
while
simultaneously increasing the feedback resistances.
There are a few advantages of this approach. First,
the feedback resistances (and their associated noise
contribution) will be reduced at low gains. Second,
the value of R
G
required to achieve high gains is
higher. The larger resistance of R
G
at maximum gain
allows a smaller C
G
for a given cutoff at maximum
gain than with a single-element control. This may
also relax requirements for end resistance in the pot
used. Third, the dual-element approach can improve
the linearity of gain vs. pot rotation compared to a
single-element solution, assuming the same taper in
the pot. Fourth, the dual-element approach lends
itself to a lower low-gain limit.
The circuit in Figure 17 has a gain range of 6 dB to
60 dB while the circuit shown in Figure 18 provides
a gain range of 4.4 dB to 60 dB. The noise behavior
of the two circuits is compared in Figure 19. Note
the superior low-gain noise performance with the
dual-element approach.
Again, other minimum and maximum gains and
noise versus gain performance can be accommodated
by selecting different values of gain resistances.
Potentiometer Limitations and Gain
Accuracy
Overall gain accuracy depends on the tolerance of
the external gain resistors and especially the
potentiometer. Theoretically, when the variable
portion of R
G
is zero for maximum gain, the gain is
determined by the feedback resistors and fixed
portion of R
G
. However, in many instances the
minimum resistance of the potentiometer (commonly
specified as end resistance) will be greater than zero
and can vary from part to part. Reducing the fixed
portion of R
G
by the amount of the end resistance
may be appropriate if the potentiometer end-
resistance is consistent. It may be easier to maintain
Applications
Figure 17. Basic Application Circuit With Variable R
G
for Gain Control, ac-Coupled R
G
+15V
5k
5k
10 3300u
10k
V+
V-
-15V
RFI
PROTECTION
R
A
R
B
R
GF
C
G
R
GV
R2
1k0
IN1
IN+
IN-
OUT+
OUT-
OUT1
OUT2
R
G
1
R
G
2
IN2
R1
1k0
C9
100n
C10
100n
THAT 1583 Low-Noise Page 9 of 16 Document 600173 Rev 03
Differential Audio Preamplifier IC
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 508 478-9200; Fax +1 508 478-0990; Web: www.thatcorp.com
Copyright © 2016, THAT Corporation; All rights reserved.
consistency at high gains with larger values of
feedback resistances, since this makes the required
value of R
G
proportionately larger for any given gain,
and minimizes the effects of end resistance. For high-
accuracy applications, consider discrete, switched
resistors for R
A
, R
B
and R
G
.
As well, take care to specify the potentiometer's
element construction to avoid excess noise.
Figure 19. Noise vs Gain of circuits in Figures 17 and 18
Figure 18. Basic Application Circuit With Variable Feedback Resistors and R
G
for Gain Control, ac-Coupled R
G
-130
-125
-120
-115
-110
-105
-100
0 10 20 30 40 50 60
[dB]
[dBu]
Figure 18
Figure 17
+15V
5k
5k
5k
3300u
5k
-15V
CW
CW
R
A
10k
R3
R
B
R
GF
10
C
G
R
GV1
R
GV2
R2
1k0
IN1
IN+
IN-
OUT+
OUT-
OUT1
OUT2
R
G
1
R
G
2
IN2
R1
1k0
R4
10k
V+
V-
RFI
PROTECTION
C9
100n
C10
100n
THAT 1583 Low-Noise Page 10 of 16 Document 600173 Rev 03
Differential Audio Preamplifier IC
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 508 478-9200; Fax +1 508 478-0990; Web: www.thatcorp.com
Copyright © 2016, THAT Corporation; All rights reserved.
Digitally Controlled Gain
In addition to analog-controlled applications, the
1583 has been designed to mate perfectly with
THAT's family of Digital Preamplifier Controller ICs
to produce an optimized, digitally controlled audio
preamplifier. THAT's digital controllers are intended
primarily for use in the feedback loop of differential,
current-feedback gain stages, such as the 1583.
Figure 20 shows a THAT5171 or 5173 Digital
Controller connected to the 1583. The controller
varies R
A
, R
B
and R
G
(from Figure 15) to produce the
desired gain based on the gain command provided
via the SPI control interface. The feedback network
impedances in these controller ICs have been chosen
to minimize noise and distortion within the com-
bined amplifier and controller at each gain step.
The controllers also include a differential servo
amplifier which minimizes the differential dc offset at
the output. The servo generates a correction voltage
at the 1583 inputs which in turn reduces the output
offset voltage. The output dc offset is controlled by
the servo amplifier inside the controller, making CG
unnecessary, and enabling a more compact PCB
design.
Please refer to the 5171 and 5173 data sheets for
more information.
Figure 21. Typical Phantom Power Application Circuit with Variable R
G
for Gain Control, ac-Coupled R
G
Figure 20. Basic Application Circuit with THAT 5171/5173 Digital Controller
R
A
R
B
R
GF
C
G
R
GV
IN1 OUT+
OUT-
OUT1
OUT2
R
G
1
R
G
2
IN2
+48V
RFI
PROTECTION PHANTOM POWER
FAULT
PROTECTION
PHANTOM POWER
R3
10
C4
47u
+
R4
10
C1
22p
C2
22p
+15V
-15V
D1
S1DB
D4
S1DB
D3
S1DB
D2
S1DB
+15V
-15V
R1
1k2
R6
6k81
R5
6k81
R2
1k2
C5
47u
+
IN+
IN- C3
220p
RFI
PROTECTION
C6
100p
5%
C7
100p
5%
C8
220p
+15V
V+
V-
-15V
5k
5k
10 3300u
10k
C9
100n
C10
100n
SYSTEM
RESET
+3.3V
+15V
Servo Resistor
Network
with FET
Switches
Control
Logic
SPI
Interface
-15V
+3.3V
THAT
5171/5173
To: Host
MCU
-
-
+
+
RG1
RG2
AGnd
IN2
IN1
SCAP2
SCAP1
SOUT1
SOUT2
SCLK
DIN
DOUT
CS
GPO1
GPO2
GPO3
GPO0
TRC
V-
Vdd
Vdd
DGnd
DGnd
BSY
RST
RB
20k
20k
RA
RG
V+
V-
V+
THAT 1583 Low-Noise Page 11 of 16 Document 600173 Rev 03
Differential Audio Preamplifier IC
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 508 478-9200; Fax +1 508 478-0990; Web: www.thatcorp.com
Copyright © 2016, THAT Corporation; All rights reserved.
Figure 22. Typical Phantom Power Application Circuit With Variable R
A
, R
B
and R
G
for Gain Control, ac-Coupled R
G
Figure 23. Typical Phantom Power Application Circuit With Digital Gain Control
Servo
RG1
RG2
AGnd
IN2
IN1
SCAP2
SCAP1
SOUT1
SOUT2
Resistor
Network
with FET
Switches
Control
Logic
SCLK
DIN
DOUT
CS
GPO1
GPO2
GPO3
GPO0
RST
TRC
V+
V+
V-
V-
Vdd
Vdd
DGnd
DGnd
BSY
THAT
5171/5173
To: Host
MCU
-
-
+
+
CW
CW
+48V
RFI
PROTECTION PHANTOM POWER
FAULT
PROTECTION
PHANTOM POWER
R3
10
C4
47u
+
R4
10
C1
22p
C2
22p
+15V
-15V
D1
S1DB
D4
S1DB
D3
S1DB
D2
S1DB
+15V
-15V
R1
1k2
R6
6k81
R5
6k81
R2
1k2
C5
47u
+
IN+
IN- C3
220p
RFI
PROTECTION
C6
100p
5%
C7
100p
5%
C8
220p
+15V
2k5
2k5
5k
8.66
3300u
5k V+
V-
-15V
R
A
10k
R10
R
B
R
GF
C
G
R
GV1
R
GV2
IN1 OUT+
OUT-
OUT1
OUT2
R
G
1
R
G
2
IN2
R11
10k
C9
100n
C10
100n
THAT 1583 Low-Noise Page 12 of 16 Document 600173 Rev 03
Differential Audio Preamplifier IC
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 508 478-9200; Fax +1 508 478-0990; Web: www.thatcorp.com
Copyright © 2016, THAT Corporation; All rights reserved.
Output Circuit Recommendations
As mentioned earlier, the THAT1583 has common-
mode gain of unity, regardless of its differential gain.
It also has a common-mode offset of approximately
one diode drop. Common-mode input signals are
presented at the output, along with the common-
mode dc offset. If these common-mode signals are
not removed, they may limit dynamic range of
subsequent stages.
If a single-ended output is desired, the THAT1246
offers a convenient way to remove common mode
offset, convert to single-ended, and match the
headroom of the 1583's output to a single-ended
drive. See Figure 24.
See DN140 which contains much additional infor-
mation and many alternative recommended solu-
tions.
Additional Resources
THAT's engineers have spent years investigating
and documenting circuit topology options, compo-
nent selection and reliability issues related to
microphone preamplifiers. We recommend the
following design notes and technical papers, which
offer additional insights into microphone preamp
design.
1. THAT Design Note 140 (DN140) "Input and
Output Circuits for THAT Preamplifier ICs"
2. "The 48 Volt Phantom Menace," by Gary K.
Hebert and Frank W. Thomas, presented at the
110th Audio Engineering Society (AES) Convention
3. "The Phantom Menace Returns" by Rosalfonso
Bortoni and Wayne Kirkwood, presented at the 127th
AES Convention.
4. "De-Integrating Integrated Circuit Preamps" by
Les Tyler, presented at the 131st AES Convention.
DN140 is of particular interest in that this design
note was intended to cover the diverse and multifac-
eted topic of integrating an amplifier/controller
combination into a fully functioning microphone
preamplifier. DN140 was written before the 1583
was released. All the circuits in DN140 reference the
THAT 1570 differential preamplifier, but all the
circuits and notes can be applied to the 1583 as well.
The circuits presented in DN140 address common
applications requirements, performance enhance-
ments, component selection, and fault protection.
DN140 should be considered an addendum to this
data sheet.
Figure 24. Simple single-ended output
1246/1256
OUT
OUT2
OUT1
SENSE
12k
12k
6k
6k
VOUT
REF
IN+
IN-
THAT 1583 Low-Noise Page 13 of 16 Document 600173 Rev 03
Differential Audio Preamplifier IC
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 508 478-9200; Fax +1 508 478-0990; Web: www.thatcorp.com
Copyright © 2016, THAT Corporation; All rights reserved.
The QFN package includes a metal thermal pad
which should be soldered to the PCB. Five thermal
vias should be arranged in the configuration shown
in Figure 25 to provide uniform heat distribution
between the top layer of the PCB to the bottom layer.
The thermal pad can be left electrically floating.
However if it is not electrically floating, it should be
connected only to V-.
For current feedback amplifiers, stray capacitance
from the R
G
pins (inverting inputs) to ground or
power planes result in higher gains at high frequen-
cies. This compromises common-mode rejection at
high frequencies and, in extreme cases, can even lead
to oscillation. Take care to avoid ground and power
planes under and near R
A
, R
B
, R
G
, their associated
pins and traces.
The input signal lines are susceptible to magnetic
pickup from power supply currents, which often take
the form of half-wave rectified versions of the signal.
Voltage fluctuations on the supply lines can couple
capacitively as well. For this reason, take care not to
run power and input signal lines close and/or parallel
to each other
Figure 25. QFN-16 Thermal Solder Pad
PCB Layout Information
0
0.45 mm
(0.018”)
1.05 mm
(0.041”)
1.65 mm
(0.065”)
2.10 mm
(0.083”)
0
0.45 mm
(0.018”)
1.05 mm
(0.041”)
1.65 mm
(0.065”)
2.10 mm
(0.083”)
Hole: 0.254 mm (0.010”)
Pad: 0.30 mm (0.012”)
THAT 1583 Low-Noise Page 14 of 16 Document 600173 Rev 03
Differential Audio Preamplifier IC
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 508 478-9200; Fax +1 508 478-0990; Web: www.thatcorp.com
Copyright © 2016, THAT Corporation; All rights reserved.
Package and So ldering Information
Figure 26. QFN-16 Surface Mount Package
Package Characteristics
Parameter Symbol Conditions Typ Units
Package Style See Fig. 26 for dimensions 16 Pin QFN
Thermal Resistance θ
JA
QFN package soldered to board
8
110 ºC/W
Environmental Regulation Compliance Complies with July 21, 2011 RoHS 2 requirements
Soldering Reflow Profile JEDEC JESD22-A113-D (250 ºC)
Moisture Sensitivity Level MSL Above-referenced JEDEC soldering profile 3
Package Order Number
16 pin QFN 1583N16-U
Table 2. Ordering Information
A
B
C
D
F
H
I
JK
Exposed
Thermal Pad
EG
0°
ITEM MILLIMETERS INCHES
A 4.00 ± 0.10 0.157 ± 0.004
B4.00 ± 0.10 0.157 ± 0.004
C 0.90 ± 0.05 0.035 ± 0.002
D0.30 ± 0.05 0.012 ± 0.002
E0.65 ± 0.05 0.026 ± 0.002
F0.40 ± 0.05 0.016 ± 0.002
G0.00 ~ 0.05 0.000 ~ 0.020
H0.20 ± 0.05 0.008 ± 0.002
I2.60 ± 0.05 0.102 ± 0.002
J 2.60 ± 0.05 0.102 ± 0.002
KC' 0.3 x 45° C‘ 0.012 x 45°
1
4
5
8
9 12
13
16
BOTTOM VIEW
THAT 1583 Low-Noise Page 15 of 16 Document 600173 Rev 03
Differential Audio Preamplifier IC
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 508 478-9200; Fax +1 508 478-0990; Web: www.thatcorp.com
Copyright © 2016, THAT Corporation; All rights reserved.
Revision History
Revision ECO Date Changes Page
00 — 10/24/12 Initial Release —
01 2827 10/01/13 Added footnote to pin assignment chart. 14
02 2912 01/26/15 Corrected the moisture sensitivity level specification. 14
03 2980 07/20/16 Change Differential Input Offset Voltage spec. Add RG Input Bias
Current and RG Input Offset Current specs. —
THAT 1583 Low-Noise Page 16 of 16 Document 600173 Rev 03
Differential Audio Preamplifier IC
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
Tel: +1 508 478-9200; Fax +1 508 478-0990; Web: www.thatcorp.com
Copyright © 2016, THAT Corporation; All rights reserved.
Notes
