OP177 Datasheet, PDF (10/12 Pages) Analog Devices – Ultraprecision Operational Amplifier

OP177
BILATERAL CURRENT SOURCE
The current sources shown in Figure 28 will supply both
positive and negative current into a grounded load.
Note that Z_O
=
R5


R4
R2
+1^{}
R5+ R4 R3
–
R2 R1
and that for Z_O to be infinite,
R5+ R4
R2
must
=
R3
R1
PRECISION ABSOLUTE VALUE AMPLIFIER
The high gain and low TCV_OS assure accurate operation with
inputs from microvolts to volts. In this circuit, the signal always
appears as a common-mode signal to the op amps. The
OP177E CMRR of 140 dB assures errors of less than 1 ppm.
See Figure 29.
Figure 30. Precision Positive Peak Detector
PRECISION POSITIVE PEAK DETECTOR
In Figure 30, the C_H must be of polystyrene, Teflon*, or
polyethylene to minimize dielectric absorption and leakage. The
droop rate is determined by the size of C_H and the bias current
of the OP41.
PRECISION THRESHOLD DETECTOR/AMPLIFIER
In Figure 32, when V_IN < V_TH, amplifier output swings nega-
tive, reverse biasing diode D₁. V_OUT = V_TH if R_L = ∞. When
V_IN ≥ V_TH, the loop closes,
( ) ^VOUT ^{= V}TH ^{+ V}IN ^–VTH
₁₊
R_F
R_S


C_C is selected to smooth the response of the loop.
*Teflon is a registered trademark of the Dupont Company.
Figure 31. Precision Threshold Detector/Amplifier
–10–
REV. B