
Typical Applications
(Continued)
R
T
e
240k
C
EXT
t
1
m
F, f
t
1 kHz
Note. The easy trim procedure is used for ac coupled input signals. It in-
volves two trims and can achieve accuracies of 2 mV offset
g
0.1% reading.
Procedure:
1. Apply 100 mV rms (sine wave) to input, adjust R3 until the output reads
100 mV
DC
.
2. Apply 5 V
rms
(sine wave) to input, adjust R4 until the output reads 5 V
DC
.
3. Repeat steps 1 and 2 until the desired initial accuracy is achieved.
FIGURE 2. LH0091 ‘‘Easy Trim’’ (For ac Inputs Only)
R1
e
dc symmetry balance
R2
e
Input offset
R3
e
Output offset
R4
e
Gain adjust
Note. This procedure will give accuracies of 0.5 mV offset
g
0.05% reading
for inputs from 0.05V peak to 10V peak.
Procedure:
1. Apply 50 mV
DC
to the input. Read and record the output.
2. Apply
b
50 mV
DC
to the input. Use R2 to adjust for an output of the same
magnitude as in step 1.
3. Apply 50 mV to the input. Use R3 to adjust the output for 50 mV.
4. Apply
b
50 mV to input. Use R2 to adjust the output for 50 mV.
5. Apply
g
10V alternately to the input. Adjust R1 until the output readings
for both polarities are equal (not necessary that they be exactly 10V).
6. Apply 10V to the input. Use R4 to adjust for 10V at the output.
7. Repeat this procedure to obtain the desired accuracy.
FIGURE 3. LH0091 Standard dc Trim Procedure
Note. The additional op amp in the LH0091 may be used as a low pass filter
as shown in Figure 4.
R1
e
R2
e
16k
C1
e
C2
e
1
m
F
f
O
j
10 Hz
TL/H/5694–6
FIGURE 4. Output Filter Connection Using the Internal Op Amp
4