19-0903; Rev 1; 2/94 General Description The MAX420, 421, 422, and 423 are a series of +15V CMOS chopper-stabilized amplifiers, designed for high accuracy amplification, signal conditioning and instru- mentation applications. These devices offer input offset and drift specification superior to previous precision bipolar amplifiers and monolithic choppers. The maxi- mum offset is 5.0uV while the guaranteed drift limit is 0.05nV/C. The combination of +15 volt operation, low power, and standard op-amp pin configuration allows these devices to virtually plug-in replace conventional lower-per- formance amplifiers. The only additional components required are two external capacitors. A wide input voltage range specification, that includes the negative supply, allows for the amplification of signals including ground in single-supply applications. The MAX420 (8 pin) and MAX421 (14 pin) have a maximum supply current of 2mA. The MAX422 (8 pin) and MAX 423 (14 pin) are low power amplifiers with a maximum current of 0.5mA. Applications Precision Amplifiers Signal Conditioning for: Thermocouples Strain Gauges, Load Cells Platinum Temperature Sensors Thermistors, Bridges High Accuracy Data Acquisition D.C. Stabilization of Amplifiers and Systems Typical Operating Circuit P a >_> QUTPUT Cexta | @ [14] INT/EXT Cexta [2] [13] EXT CLK IN NC(GUARO) [3] snaxian [72] INT CLK OUT -INPUT 4] MAxX427 fil vt OF Olu +INPUT [8] MAx423 [0] OUTPUT NC(GUARD) [6] [3] OUTPUT CLAMP V-D 8] CRETN NC = No internal connection. Inverting Amplifier | (Pin Configurations continued on last page) | SA AALSVI __ 15 Volt Chopper Stabilized Operational Amplifier Features 5uV Max Offset Voltage +15V Supply Operation Input Voltage Range: +11V to -15V Low Input Noise: 0.3yV, - ) (DC - 1Hz) High Gain, CMRR, PSRR: 120dB Low Power CMOS Design: 0.5mA Max Supply Current (MAX422/423) *'e+ @ Oe @ @ Low Input Bias Current: 30pA Max Ordering Information PART TEMP. RANGE PACKAGE MAX420CPA 0C to +70C 8 Lead Plastic DIP MAX420EPA -40C to +85C 8 Lead Plastic DIP MAX420MTV -85C to +125C TO-99 Metal Can MAX421CPD oC to +70C 14 Lead Plastic DIP MAX421 CWE 0C to +70C 16 Lead Smal! Outline MAX421C/D OC to +70C Dice MAX421EPD -40C to +85C 14 Lead Plastic DIP MAX421MJD -55C to +425C 14 Lead CERDIP (Ordering information continued on last page) ___ Pin Configurations Top View tom 0] e (a | Cexte -INPUT[2]| *4AxIm yr (| MAX420 a +INPUT [3] MAX422 [6] OUTPUT v- | [5] CRETN MAXLVI MAKI 1S a registered trademark of Maxim Integrated Products. Maxim integrated Products 1 ESbh/eSSh/LSob/OCPXVNMAX420/421/422/423 +15 Volt Chopper Stabilized Operational Amplifier ABSOLUTE MAXIMUM RATINGS Total Supply Voltage (V*tOV-) 2... cece cece cece eens 36V Input Voltage ...... eee ee eee (V* + 0.3) to (V-- 0.3) V Storage Temperature Range .............0005 -65C to +160C Operating Temperature Range ............000ee uae See Note 1 Lead Temperature (Soldering, 10 sec) ..............06- +300C Voltage on Oscillator Control Pins ..............000008 Vr to Vo Duration of Output Short Circuit ............0 cece ee Indefinite Current Into Any Pin wo... eee cee eee eee e eee e eens 10mA Continuous Total Power Dissipation (T, = +25C) CERDIP Package ............ 0c ccc eee eee eee ees 500mW Plastic Package ..... 0... ccc cece erence eee 375mW TO-99 2 cect cece eee tebe e eee eee 250mW Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or any other conditions above those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS MAX420, MAX421 (Vt = +15V, V- = -15V, Ta = +25C. Test circuit unless noted.) PARAMETER SYMBOL CONDITIONS MIN. TYP. MAX. UNITS _ Cc +1 +10 Ta = 728C EM H +5 HV Input Offset Voltage Vos Over Temperature Cc +2 +20 Vv Range (Note 1, 2) E.M +2 +10 # Average Temperature AV Coefficient of Input Sos ner a (Note 12) EM 0.02 0.08 ue Offset Voltage aT 9 _ c 10 100 Ta = 725C EM 10 30 pA Input Bias Current Ip c 30 pA cee Temperature E s PA M 0.5 5 nA = Cc 15 200 Ta = 725C EM 15 80 pA Input Offset Current los Over Temperature Cc 30 pA Ran Not 1) E 50 pA ange (Note M 0.5 10 nA Input Resistance Rin 1072 (9) - . Ry = 10k0, Voyy = 10V, Ty = +25C 120 150 Large Signal Voltage Gain Avot Over Temperature Range (Note 1) 120 150 dB . CLAMP not R_ = 10k0, +12 +14.5 Output Voltage Swing Vout connected (note 3) Ry = 100k +14.95 v Common-Mode Voltage Range CMVR / +11, -15 +11.5, -15.1 Vv Common-Mode omar CMVR = +11V to -15V, TA = +25C 120 140 dB Rejection Ratio Over Temperature Range (Note 1) 110 140 Power Supply PSRR +3V to +16.5V, Ta = 25C 120 140 dB Rejection Ratio Over Temperature Range (Note 1} 110 140 Input Noise Voltage - (P-P value not exceeded en Rg = 1000, be e lode HVp-p 95% of time) pp : Input Noise Current In f = 10Hz 0.01 pA/\Hz Unity-Gain Bandwidth GBW 500 kHz Slew Rate SR C, = 50pF, AR, = 10k 0.5 VW/ us Rise Time t 0.7 MS Overshoot 20 % Note 1: Operating temperature range for 'C" parts is 0C to +70C, for "E parts is -40C to +85C, and for M parts is -55C to +125C. Note 2: Guaranteed by design. Note 3: The OUTPUT CLAMP pin 9 on MAX421, when connected to the inverting input (pin 4), reduces the overload recovery time inherent with chopper-stabilized amplifiers (see text). Note 4: All pins are designed to withstand electrostatic discharge (ESD) levels in excess of 2000V (Mil Std 883C, Method 3015.2 Test Circuit). 2 MAAI/VI+15 Volt Chopper Stabilized Operational Amplifier ELECTRICAL CHARACTERISTICS MAX420, MAX421 (continued) (V* = +15V, V- = -15V, Ta = +25C. Test circuit unless noted.) PARAMETER SYMBOL CONDITIONS MIN. TYP. MAX. UNITS Operating Supply Range Vive +2.5 416.5 Vv | Supply Current Is Seer ternperature Range (Note 1) "8 35 mA Internal Chopping Frequency fon Pins 12-14 Open (MAX421) 400 Hz Clamp ON Current (Note 3) love (ony | Ry = 100k 25 100 BA Clamp OFF Current (Note 3) Vote corr) | -10V S Vour = +10V 1 pA Offset Voltage vs. Time 100 nV/\/month Note 1: Note 2: Guaranteed by design. Note 3: inherent with chopper-stabilized amplifiers (see text). Note 4: Circuit). SUPPLY CURRENT vs. TEMPERATURE 20 zis = MAXA20. 421 = > 10 & a 0 -50 -2 0 2 S80 75 IDO 125 TEMPERATURE (C) INPUT VOLTAGE RANGE vs. SUPPLY VOLTAGE 16 4 MAX420 2 MAXa21 = MAX422 5 MAX423 z & 2 8 SF s se $ Ss 5 S : a 4 2 0 2 4 6 8 WwW 12 4 = 16 + AND SUPPLY VOLTAGE [V) y MAXI/VI SUPPLY CURRENT (mA) * DFESET VOLTAGE. ) 20 05 SUPPLY CURRENT vs. SUPPLY VOLTAGE MAX420. 421 MAX422, 423 2 4 6 8 W 2 4 16 + AND SUPPLY VOLTAGE {V) INPUT OFFSET VOLTAGE vs. SUPPLY VOLTAGE MAX420 MAX421 MAX422 MAX423 NN 4 6 8 io 612) =(14 16 + AND SUPPLY VOLTAGE [V] Operating temperature range for C parts is OC to +70C, for E parts is -40C to +85C, and for M parts is ~55C to +125C. The OUTPUT CLAMP pin 9 on MAX421, when connected to the inverting input (pin 4), reduces the overload recovery time All pins are designed to withstand electrostatic discharge (ESD) levels in excess of 2000V (Mil Std 883C, Method 3015.2 Test Typical Operating Characteristics ESh/SSh/Leov/OCHUXVNMAX420/421/422/423 +15 Volt Chopper Stabilized Operational Amplifier ABSOLUTE MAXIMUM RATINGS: same as for MAX420, 421 ELECTRICAL CHARACTERISTICS MAX422, MAX423 (Vt = +15V, V- = -15V, Ty = +25C. Test circuit unless noted.) PARAMETER SYMBOL CONDITIONS MIN. TYP. MAX. UNITS c +1 +10 Ta = 425C EM 4 +5 HV input Offset Voltage Vos Over Temperature Cc +2 +20 T p _ = uV Range (Note 1, 2) E.M +2 +10 Average Temperature Vv Coefficient of Input Vos over Ne EM 0.02 0.05 uW/C Offset Voltage aT g , Cc 10 100 Ta = +25C pA Input Bias Current A EM 10 30 (Doubles every 10C lp Cc 30 pA above about 60C) Beer aonperature E 35 pA ange (Note 1) M 0.5 5 nA Cc 15 200 Ta = +25C pA Input Offset Current A EM 15 60 (Doubles every 10C los Cc 30 pA above about 60C) eer aonperature E 50 pA ange (Note 1) M 0.5 10 nA Input Resistance Rn 1072 o . ; Ry = 100kQ), Voyy = 10V, Ty = +25C | 120 150 Large Signal Voltage Gain Avot Over Temperature Range (Note 1) 120 150 dB Output Voltage Swing Vour nie connected (Note 3) +14 +146 Vv Le Common-Mode Voltage Range CMVR +11, -15 +11.5, -15.4 v Common-Mode CMRR CMVR = +11V to -15V, TA = +25C 120 4140 4B Rejection Ratio Over Temperature Range (Note 1) 110 140 Power Supply PSRR +3V to +16.5V, T, = +25C 120 140 dB Rejection Ratio Over Temperature Range (Note 1) 110 140 Input Noise Voltage - (P-P value not exceeded en Rg = 10022, DC to thi 0.4 Vo . p-p DC to 10Hz 1.2 oP 95% of time) Input Noise Current In f = 10Hz 0.01 pA/V/Hz Unity-Gain Bandwidth GBW 125 kHz Slew Rate SR C, = 50pF, R, = 100k 1.25 V/s [Rise Time t, 28 us Overshoot 20 % Operating Supply Range Vive 42.5 +165 Vv No Load, Ty = +25C 0.3 0.5 Supply Current 's Over Temperature Range (Note 1) 1 mA Internal Ghapping Frequency fon Pins 12-14 Open (MAX423) 250 Hz Clamp ON Current (Note 3) locp ron, | RL = 1MQ 5 25 HA Clamp OFF Current (Note 3) loLe torr) | ~10V S Vout S +10V 1 pA Offset Voltage vs. Time 100 nv/\/month Note 1: Operating temperature range for C parts is 0C to +70C, for E parts is -40C to +85C, and for M parts is -55C to +125C. Note 2: Guaranteed by design. Note 3: The OUTPUT CLAMP, pin 9 on MAX423, when connected to the inverting input (pin 4), reduces the overload recovery time inherent with chopper-stabilized amplifiers (see text). Note 4: All pins are designed to withstand electrostatic discharge (ESD) levels in excess of 2000V (Mil Std 883C, Method 3015.2 Test Circuit). MAAKIM+15 Volt Chopper Stabilized Operational Amplifier INPUT OFFSET VOLTAGE vs. CLOCK FREQUENCY ; MAXA21 MAX423 S 6 = 3 - Bo 2 0 10 100 1K 10K GLK OUT FREQUENGY (Hz) {CLK OUT = Ye CLK IN) CLOCK FREQUENCY vs. SUPPLY VOLTAGE 400 z -_ MAX420, 421 = = ae 8 = 20 MAX422, 423 100 2 4 6 8 OW 2 MW 1B + AND SUPPLY VOLTABE {V1 MAXIMUM OUTPUT CURRENT vs. SUPPLY VOLTAGE 4 _ 3 z E 2 @ 5 1 ow 5 E 0 = -10 2 = = -20 = 3) -a0 2 4 6 8 10 2 14 16 + AND - SUPPLY VOLTAGE [) MAAXLYVI CLOCK FREQUENCY (Hz) Typical Operating Characteristics P-P NOISE VOLTAGE vs. CLOCK FREQUENCY P-P NOISE [VI MAX421 MAX423 OC to 19Hz 100 IK 10K CLK OUT FREQUENCY (Hz} (CLK OUT = % CLK IN) CLOCK FREQUENCY vs. TEMPERATURE MAX420, 421 MAX422, 423 -0 -25 0 2 8 75 100 125 TEMPERATURE (C) CLOCK RIPPLE REFERRED TO THE INPUT vs. TEMPERATURE P-P CLOCK RIPPLE (::4} MAX420 MAX421 MAX422 MAX423 -50 -25 0 25 50 75 100 125 TEMPERATURE (C) ESP/eSch/tLev/OcCrXVNMAX420/421/422/423 +15 Volt Chopper Stabilized Operational Amplifier Typical Operating Characteristics FOLLOWER LARGE SIGNAL PULSE RESPONSE, MAX420, 421 + 10 OUTPUT (VOLTS) os I s 0 20,:8/DIVISION FOLLOWER LARGE SIGNAL PULSE RESPONSE, MAX422, 423 0 20..8/DIVISION OPEN LOOP GAIN AND PHASE SHIFT vs. FREQUENCY OPEN-LOOP GAIN (dB) MAX420, 421 ~~~ MAX422, 423 & PHASE SHIFT (DEGREES) a | 10100 FREQUENCY (Hz) 10K 100K 1M Detailed Description Amplifier Operation A block diagram of a MAX420 series amplifier is shown in Figure 2. Internally there are two amplifiers, a main amp and a nulling amp. The main amplifier is in the primary signal path and is continuously con- nected to the external inputs. The null amp alternately corrects its own offset, and then that of the main amp, as its input switches between the two main amp inputs. Offset correction is accomplished by means of compensating FETs in the input stages bias circuitry (not shown). The offset values that drive these trim FETs are stored for the duration of the correction cycle on two capacitors, Cexm and Cexrs. Each cycle is controlled by the clock as shown in the timing diagram of Figure 2. An added benefit of the offset correction scheme is that it also increases CMRR, PSRR, and Avo. at low frequencies (fin < fcuk). Capacitor Selection Two external capacitors, Cexta and Cextp, connected as shown in Figure 1, enable the amplifier to store and correct its own offset errors. The MAX420 series is specified with 0.1uF capacitors, however, other values up to 1.0uF may be optimal if different clock rates are used (MAX421, 423 only). If an external clock is used, the capacitor values should be scaled to roughly maintain the ratio between the nominal self-clock period (2.5ms @ 400Hz) and 0.1yF. For example, if a 200Hz clock were used, then 0.2uF would be best. This relationship is not critical and certainly no change in capacitor value is necessary for part-to-part variations in the internal clock rate. MAAL/VI+15 Volt Chopper Stabilized Operational Amplifier Ry AAA WY 1k QUTPUT Our Our INT/EXT o- 4 A exreikiwo | ose. [74 } 8 CLK OUT o ee r] acre [= DUTPUT ~ CLAMP co i @+ 1, 5 I eons +IN -IN O- a Aes) CAP nerunn Cexta a 7. Ty MAXIM _ - MAX420 MAX421 MAX422 SLI LS exteikn MAX423 | A= CLK OUT FL a B J Lt Figure 1. Test Circuit. The banded or outer foil end of the correction capacitors should be connected to Cretn as this is a low impedance point. Cexja and Ceytgare high impedance nodes and so the connections to these pins should be as short as possible to minimize noise pick-up. Capacitor Types Precision DC performance can be realized with a wide variety of capacitor types, however those with high leakage will cause excessive clock ripple in the signal path and should not be used. Other low cost capacitors, such as ceramics, may have adequate leakage specifi- cations but often also exhibit high dielectric absorption. This will not harm the amplifiers DC performance but can increase the initial settling time on turn-on to 1o0r2 seconds (to 1uV). If fast settling after power-up is required then higher quality capacitors, such as mylar or polypropylene, should be used. Clock Anon-chip clock is included on all 420 series amplifiers to control the operation of the offset correction circuitry. This oscillator is completely self contained and needs no external components or connections. The internal clock rate is nominaly 400Hz on the MAX420/421 and is 250Hz on the MAX422/423. External Clock The MAX421 and 423 have an INT/EXT pin for clock selection (pin 14). The pin has an internal pull-up and, for self-clocked operation, can be left open or connected MAXI Figure 2. Maxim MAX420 Series Amplifier Block Diagram. to V+. When INT/EXT is tied to V- the internal clock is disabled and an external clock can then be applied to EXT CLK IN. Because of an internal divider, the offset nulling circuitry runs at one half the external clock rate. Duty Cycle and Thresholds The duty cycle of the external clock is not critical at low frequencies. For EXT CLK IN frequencies of 500Hz or greater, a 50% to 80% positive duty cycle is recom- mended to allow transients on the null capacitors to settle. This is necessary because the capacitors are only charged when EXT CLK IN is high. The input threshold for EXT CLK IN is typically V+ - 2.5V so that an external clock signal can swing from either V+ to GROUND or V* to V-. The internal chopping frequency is available at the CLK OUT pin with either internal or external clock operation .The nominal output levels for CLK OUT are V* for a High and V* - 5V for a clock Low. In some instances, it may be advantageous to syn- chronize two amplifier clocks, or slave one to another. A simple way to accomplish this is to tie the amplifiers EXT CLK IN pins together (MAX421 or 423 only) and pull ones INT/EXT pin low while allowing the other's to float high. The amplifier with INT/EXT high will then provide the clock for both devices (see Figure 9). ESb/ech/tev/OcrxvVNMAX420/421/422/423 +15 Volt Chopper Stabilized Operational Amplifier OtuF INPUT QUTPUT FOR CLAMP EFFECT Vin = Ay + Ag > icuP (On) INPUT OjeF OIF FOR CLAMP EFFECT Vn IeLP (om) Ry + Rg> Figure 3. Non-inverting Amplifier with Optional Clamp. Plugging into a Conventional Op-Amp Socket As a result of their +15V supply capability, the 8-pin MAX420 and 422 can plug directly into a conventional op-amp socket for immediate upgrading of DC specifi- cations. Since the external nutling capacitors occupy what are usually Offset null pins (1, 5, and 8), the standard op-amp pin-out is still maintained for input, output, and supply connections. Essentially, Cexta and Cextg replace the offset trim pot normally required with conventional op-amps. Output Clamp/Overload The OUTPUT CLAMP, when connected to the inverting input, reduces the amplifiers overload recovery time (see Figures 3 and 4). It does this by providing a feedback path that is activated just before the output saturates. The resultant reduction in gain prevents differential input overload and consequent charge build-up on the correction capacitors. If the capacitors are allowed to overcharge, the amplifier will need time to recover (typically 500ms) after the overload is removed. Since the OUTPUT CLAMP activates slightly prior to output saturation there is also a small reduction in output swing when it is used. This reduction is typically 500mV with a 10k2 output load. Single Supply Operation The 420 series amplifiers are well suited for operation in single power supply applications that have system ground connected to V-. With supply voltages of 10 volts or above the input range is typically from Ground to V* - 1.5V. At lower supply voltages the input-range lower limit will be higher (approx. Gnd + 0.5V at 5V supply). The amplifiers outputs will swing to within approximately 50mV of Ground or Vt with a 100k load and within 500mV with 10k (MAX420, 421 only). Figure 4. Inverting Amplifier with Optional Clamp. Applications Low Voltage Signals Realizing microvolt offset and nanovolt drift perfor- mance goes beyond the selection of a precision ampli- fier (though it's not a bad start). When trying to amplify very low level signals any number of outside error sources can confuse the measurement. These errors are often indistinguishable from real signal or amplifier error, which of course is why they are a problem. Thermo-Electric Effect This property describes how thermocouples measure temperature. In short it states that two dissimilar metals in contact can be expected to generate a voltage. This is fine for thermocouples but is not so useful when pin-to-socket, socket-to-circuit board, and circuit board- to-edge connector junctions all generate signals which can add to input error. The voltage generated in such situations can range from 0.1 to 10s of uV/C, many times the offset drift of an MAX420. In general such problems are dealt with by minimizing sockets and connectors in low level circuitry and by using com- ponents designed for low thermal EMF when connec- tors, relays, etc. are unavoidable. Gradients The presence of heat in low level circuitry is often not so much a problem as are thermal gradients. Gradients can, for example, cause normally balanced amplifier input connections to be at different temperatures. These connections then generate different thermoelec- tric voltages that can no longer be completely cancelled by the balanced inputs. The moral then is to minimize thermal gradients by keeping power dissipation and air currents in and around low level circuitry and connec- tions at a minimum. MAAILM@I+15 Volt Chopper Stabilized Operational Amplifier MAXIM Re INPUT QUTPUT Inverting Amplifier Follower * Use Rg for thermal balancing of inputs, or for clamp. MAX 420, 421, 422, 423 EXTERNAL CAPACITORS Ro /\ % Nt; OUTPUT OUTPUT ayy, 7 8 Ri EXTERNAL 5 CAPACITORS 4 INPUT 4 ey ve s GUARD SS Non-Inverting Amplifier Bottom View should be low Board Layout for Input __R1R2_ impedance for Guarding with TO-99 Note: : . : R,+ Ro optimum guarding Package, Bottom View Figure 5. input Guard Connections. Thermal Symmetry Another useful low level technique is to design thermal symmetry into the layout. This may mean adding dummy resistors and connections so that the thermal mass, as well as the number of thermoelectric error sources, in an input pair will cancel. It may also involve running input traces near each other and keeping their size the same as well. Thermal filtering with small enclosures or even insulation for sensitive areas can also be helpful. Low Current Signals, input Guards Low leakage, high impedance CMOS inputs allow the MAX420 amplifier family to amplify the signals of very high impedance sources. Though the amplifiers input bias current is measured in picoamps, getting the surrounding connections to live up to that specification requires some attention. In applications where picoamp or nanoamp errors can be significant, board leakage either from surface contamination or through the board material itself may be a problem. Controlling Leakage Using low leakage board materials and proper cleaning methods after assembly can provide marked reductions in leakage induced errors. Beyond this, conformal coatings can be used to control later surface contami- nation. In some cases, Teflon insulators and/or circuit board guard rings may be necessary to protect very high impedance nodes. Guard connections for various amplifier configurations are shown in Figure 5. In each case the guard is connected to a low impedance point that is approximately at the same potential as the inputs. Leakage currents from other points on the board are then absorbed by the guard. For best results, guard rings should be used on both sides of the circuit board. The 14 pin MAX421 and 423 have specifically been designed to ease input guard layout in that the pins adjacent to the inputs are unused in those packages. MAAN Output Characteristics /Open Loop Gain The MAX420 and 421 can typically drive a 10kO load from +14.8V to -14.5V when operating with +15V power supplies. With a 100k or greater load, however, the output can typically swing to within 50mvV of each rail. The output swing with the lower power MAX422 and 423 will be somewhat less for a given load. The open loop gain of a MAX420 series amplifier is somewhat load dependent for resistances which are less than 10k. The effect is largely due to the impedance of the amplifiers output stage. The gain is about 17dB lower with a 1k load than it is with 10kQ. Since even with 1kQ the gain is still typically 120dB, the reduction is insignificant for low frequency applications. In wideband circuits, however, the best results are achieved with loads of 10kM or more where the amplifiers open loop response is asmooth 6dB/octave slope from 0.1Hz to 0.5MHz. Additionally, there is negligible phase shift at the frequency where the null amp Is rolled off. Intermodulation In some chopper-stabilized amplifier designs, inter- action between the input signal and the chopper frequency sometimes produces intermodulation prod- ucts in the form of sum and difference signals. If the input frequency and the chop rate are near enough to each other, a difference signal may even appear as a DC error at the output. The MAX420 series minimizes these problems with active compensation circuitry that virtually eliminates intermodulation effects and controls the amplifier's open loop gain-phase characteristics as well. With well behaved open loop parameters, the chopper circuitrys impact on the amplifiers dynamic performance can be ignored in most applications. | SP/SShr/leov/OcCrXVWMAX420/421/422/423 +15 Volt Chopper Stabilized Operational Amplifier Typical Applications 100kKQ. 10002 +15V Note 1: Note 2: Shunt contact point determined at calibration. QiyF ObuF 0019 SHUNT (Fy) == SUPPLY GROUND R, = 3 cm. #20 Lt. QUTPUT 1V/AMP INSTRUMENT GROUND solid copper wire. + OR 10 REFERENCE O 12-BIT CMOS 0-T0A MAKI MAX423 OUTPUT C oO 0 T0 -Vrer OluF Our Figure 6. Ultra-low Current Shunt Amp. Figure 7, CMOS DAC Output Amplifier. Low offset maintains DAC linearity. Note Note Note Note PONS A220 4 10k (84.9k0) +15 THERMAL CONTACT Q, and connection terminals must be at the same temperature. Values in parentheses are for type K thermocouple. Connections to inverting input of op-amp should be kept as short as possible to reduce noise pickup. All circuit power is +15V. OluF Our 1kN O -15V MAXIM ICL8069 |.2v lom/C @ 25C lamv/C @ 750C _o OUTPUT lomv/ C @ 25C lemv/C @ 1000C: Figure 8. Amplitier with Coid-Junction Compensation for Grounded Thermocouples. 10 MAXIM+15 Volt Chopper Stabilized Operational Amplifier Typical Applications JOV BRIDGE ORIVE 100k) mT 3500 amv/V 100k OtuF I OF Olek c + CR MAXIM Ae MAX421 INT/ AC. Ra 100ka. AAA, MWA , $m 2 Ry ; 150K2) $ 100kKQ NOTE 3 Re MAKIN ; 9098) O Vout + MAXOPOZ, IOV ES. ~TaV CLK A) MAXIM MAX421 C + CR t OtuF O1peF Rg 150k aque yy. Ra BAIN = (U+ Fd - 100k, Ry Ry 100K22 Note Note Note Note Note : Matching rules: R, =Rgand R7 Rs Metal film or wire-wound resistors are recommended. A,s internal clock is slaved to A, via CLK IN pins. All amplifiers powered from +16V supplies. : Ry is a selected value. Re _ Ra . Matching determines CMAR, for example 0.1% = 60dB, 0.01% = 800B. Figure 9. 10uV Vos, O.1uW/C Strain Gauge Instrumentation Amplifier. Chip Topography +15 VOLTS Bin OW 100k Q Reopk Figure 10. D.C. Stabilized Power Op-Amp. Main amp has 5MHz unity-gain point. MAAIM INT CLK OUT Geeta INT/EXT | EXT CLE IW _| MAXIM 2 AMP LH0101 OUTPUT ouTeuT ior" (272mm) Dw DF PUT 15 VOLTS QUTPUT CLAMP | tain) | Ecb/ecr/ler/OcrXVNMAX420/421/422/423 +15 Volt Chopper Stabilized Operational Amplifier __ Ordering Information (continued) PART TEMP. RANGE PACKAGE MAX421M/D -85C to +125C Dice MAX422CPA 0C to +70C 8 Lead Plastic DIP MAX422EPA -40C to +85C 8 Lead Plastic DIP MAX422MTV -55C to +125C TO-99 Metal Can MAX423CPD 0C to +70C 14 Lead Plastic DIP MAX423CWE 0C to +70C 16 Lead Small Outline MAX423C/D 0C to +70C Dice MAX423EPD -40C to +85C 14 Lead Plastic DIP MAX423MJD -85C to +126C 14 Lead CERDIP MAX423M/D -55C to +125C Dice ____ Pin Configurations (continued) Cexra | 9 ad [16] INTEXT Cex | [15] EXT CLK IN NC (GUARD) [3 | MAXIM [14] INT CLK OUT -iNpuT [4] = MAX421" [fia] v* sinpuT [5] MAX423" [12) OUTPUT NC (GUARD) [6 | [7] OUTPUT CLAMP vo 4 70] CRETN ne [8] r9 ] NC NC = No internal connection * Pinout for small outline package only Maxim cannol assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any lime. 12 Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408} 737-7600 1994 Maxim Integrated Products Printed USA MAAXIMA js a registered trademark of Maxim Integrated Products.