REV. A
PKD01
–12–
APPLICATIONS INFORMATION
Optional Offset Voltage Adjustment
Offset voltage is the primary zero scale error component since a
variable voltage clamp limits voltage excursions at D1’s anode
and reduces charge injection. The PKD01 circuit gain and opera-
tional mode (positive or negative peak detection) determine the
applicable null circuit. Figures 5 through 8 are suggested circuits.
Each circuit also corrects amplifier C offset voltage error.
A. Nulling Gated Output gm Amplifier A. Diode D1 must
be conducting to close the feedback circuit during amplifier A
VOS adjustment. Resistor network RA – RC cause D1 to conduct
slightly. With DET = 0 and VIN = 0 V, monitor the PKD01
output. Adjust the null potentiometer until VOUT = 0 V. After
adjustment, disconnect RC from CH.
B. Nulling Gated gm Amplifier B. Set Amplifier B signal
input to VIN = 0 V and monitor the PKD01 output. Set DET =
1, RST = 1 and adjust the null potentiometer for VOUT = 0 V.
The circuit gain—inverting or noninverting—will determine which
null circuit illustrated in Figures 5 through 8 is applicable.
PKD01
D1
CH
1000pF
C
A
B
VOUT
VS–
VS+
0.1 F
DET
R1
1k
RST
–15V
RC
2M
RA
200k
RB
1k
NOTES:
1. NULL RANGE =
VS
( )
2. DISCONNECT RC FROM CH AFTER AMPLIFIER A ADJUSTMENT.
3. REPEAT NULL CIRCUIT FOR RESET BUFFER AMPLIFIER B IF REQUIRED.
RA, RB AND RC NOT NECESSARY FOR AMPLIFIER B ADJUSTMENT.
VIN+
R1
1k
R2
2M
100k
R1
R2
Figure 5. VOS Null Circuit for Unity Gain Positive Peak
Detector
PKD01
D1
CH
1000pF
C
A
B
VOUT
R2 = R3 + R4
VS–
VS+
25k
R4
20
0.1 F
DET
R1
RST
–15V
RC
2M
RA
200k
RB
1k
NOTES:
1. NULL RANGE =
VS
( )(
)
2. DISCONNECT RC FROM CH AFTER AMPLIFIER A ADJUSTMENT.
3. REPEAT NULL CIRCUIT FOR RESET BUFFER AMPLIFIER B IF REQUIRED.
R1
VIN–
VIN+
R5
20k
R3
R5
R4
R1
R1 + R3
Figure 6. VOS Null Circuit for Differential Peak Detector
PKD01
D1
CH
1000pF
C
A
B
VOUT
R2
VIN
R1
0.1 F
VS–
VS+
25k
DET
R3
20k
RST
–15V
RC
2M
RA
200k
RB
1k
NOTES:
1. NULL RANGE =
VS
( )
2. DISCONNECT RC FROM CH AFTER AMPLIFIER A ADJUSTMENT.
3. REPEAT NULL CIRCUIT FOR RESET BUFFER AMPLIFIER B IF REQUIRED.
R4
R3
R4
20
Figure 7. VOS Null Circuit for Negative Peak Detector
PKD01
D1
CH
1000pF
C
A
B
VOUT
R2
VIN
R1
R5
20k
R3
20
0.1 F
VS–
VS+
25k
DET
R4 = R2 R1
R1 + R2
R4
RST
–15V
RC
2M
RA
200k
RB
1k
GAIN = 1 +
R2
R1 + R3
NOTES:
1. NULL RANGE =
VS
( )
2. DISCONNECT RC FROM CH AFTER AMPLIFIER A ADJUSTMENT.
3. REPEAT NULL CIRCUIT FOR RESET BUFFER AMPLIFIER B IF REQUIRED.
R3
R5
Figure 8. VOS Null Circuit for Positive Peak Detector with
Gain