Datasheet AD706 (Analog Devices) - 7

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AD706 10k +VS + 0.1 F 10k VIN – 8 VOUT 1/2 AD706 + 4 RL CL 2.5k SQUARE 0.1µF WAVE INPUT –VS
Figure 5a. Unity Gain Inverter Connection Figure 5b. Unity Gain Inverter Large Figure 5c. Unity Gain Inverter Small Figure 5d. Unity Gain Inverter Small Signal Pulse Response, CL = 1,000 pF Signal Pulse Response, CL = 100 pF Signal Pulse Response, CL = 1000 pF Figure 6 shows an in-amp circuit that has the obvious advantage CMR is still dependent upon the ratio matching of Resistors R1 of requiring only one AD706, rather than three op amps, with through R4. Resistor values for this circuit, using the optional subsequent savings in cost and power consumption. The transfer gain resistor, RG, can be calculated using function of this circuit (without RG) is R1 = R4 = 49.9 kΩ  R4  V = V ( − V ) 1 + R2 = R3 = 49.9 kΩ OUT IN1 IN2  R3 0.9 G −1 for R1 = R4 and R2 = R3. R = 99.8 kΩ G 0.06 G Input resistance is high, thus permitting the signal source to have an unbalanced output impedance. where G = The desired circuit gain. Table I provides practical 1% resistance values. Note that
R RG (OPTIONAL)
without resistor R
G (OPTIONAL)
G, R2 and R3 = 49.9 kΩ/G–1.
R1 R1 R2 R2 R3 R3 R4 R4 Table I. Operating Gains of Amplifiers A1 and A2 and 49.9k 49.9k 49.9k 49.9k +V +VSS Practical 1% Resistor Values for the Circuit of Figure 6 0.1 0.1 FF 1/2 1/2 8 8 2 2 – – Circuit Gain Gain of A1 Gain of A2 R2, R3 R1, R4 AD706 AD706 A1 R A1 1 5 + R 1 5 – P* P*
1.10 11.00 1.10 499 kΩ 49.9 kΩ
V V 3 A2 7 IN1 IN1 3 + A2 7 + 1k 1k 1/2 1/2 OUTPUT OUTPUT
1.33 4.01 1.33 150 kΩ 49.9 kΩ
6 – AD706 6 + 4 AD706 4
1.50 3.00 1.50 100 k
R
Ω 49.9 kΩ
RP* P* V VIN2 IN2 0.1 0.1 FF
2.00 2.00 2.00 49.9 kΩ 49.9 kΩ
1k 1k –V –VSS
10.1 1.11 10.10 5.49 k
R4 2R4
Ω 49.9 kΩ
R4 V 2R4 VOUT = (V OUT = (VIN1 – V IN1 – VIN2) (1+ ) + ( ) IN2) (1+ ) + ( ) R3 R3 R R FOR R1 FOR R1 = R4 = R4, R2 , R2 = R3 G = R3 G
101.0 1.01 101.0 499 Ω 49.9 kΩ 1001 1.001 1001 49.9 Ω 49.9 kΩ
* OPTIONAL INPUT PROTECTION RESISTOR FOR GAINS GREATER *OPTIONAL INPUT PROTECTION RESISTOR FOR GAINS GREATER THAN 100 OR INPUT VOLTAGES EXCEEDING THE SUPPLY VOLTAGE. THAN 100 OR INPUT VOLTAGES EXCEEDING THE SUPPLY VOLTAGE.
For a much more comprehensive discussion of in-amp applica- Figure 6. Two Op Amp Instrumentation Amplifier tions, refer to the Instrumentation Amplifier Applications Guide— Furthermore, the circuit gain may be fine trimmed using an available free from Analog Devices, Inc. optional trim resistor, RG. Like the three op amp circuit, CMR increases with gain, once initial trimming is accomplished—but REV. G –7– Document Outline FEATURES APPLICATIONS CONNECTION DIAGRAM GENERAL DESCRIPTION PRODUCT HIGHLIGHTS SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS METALIZATION PHOTOGRAPH TYPICAL PERFORMANCE CHARACTERISTICS 1 HZ, 4-POLE, ACTIVE FILTER OUTLINE DIMENSIONS ORDERING GUIDE REVISION HISTORY