Data Sheet

SSM2018

Rev. C | Page 15 of 16

If a symmetry trim is to be performed, it should precede the

control feedthrough trim and be done as follows:

1. Apply a 1 kHz sine wave of 10 dBu to the input with the

control voltage set for unity gain.

2. Adjust the symmetry trim potentiometer to minimize

distortion of the output signal.

Next, the control feedthrough trim is done as follows:

1. Ground the input signal port and apply a 60 Hz sine wave

to the control port. The sine wave should have its high and

low peaks correspond to the highest gain to be used in the

application and 30 dB of attenuation, respectively. For

example, a range of 20 dB gain to 30 dB attenuation

requires that the sine wave amplitude ranges between

−560 mV and +840 mV on Pin 11.

2. Adjust the control feedthrough potentiometer to null the

signal seen at the output.

Figure 34. OVCE Follower/VCA Connection

Figure 35. OVCE Application Circuit

VOLTAGE CONTROLLED PANNER

An interesting circuit that is built with the OVCE building

block is a voltage controlled panner. Figure 36 shows the

feedback connection for the circuit. Note that the average of

both outputs is fed back to the input. Thus, the average must be

equal to the input voltage. When the control voltage is set for

amplified. The result is that the control voltage causes the input

to pan from one output to the other. The following expressions

show how this circuit works mathematically:

(4)

where K varies between 0 and 1 as the control voltage is

changed from full attenuation to full gain, respectively.

trimming is required for best performance. Pin 9 must be

grounded. This is possible because the feedback is constant and

the adaptive network is not needed. The VCP is the only

application shown in this data sheet where Pin 9 is grounded.

Figure 36. Basic VCP Connection

1

V+

+

–

2

3

4

V–

1µF

NC

SYMMETRY

TRIM

CONTROL

FEEDTHROUGH

TRIM

1kΩ

18kΩ

NOTES

1. RB = 30kΩ FOR CLASS A.

150kΩ FOR CLASS B.

2. NC = NO CONNECT.

470kΩ

18kΩ

10MΩ

500kΩ

INPUTS

V+

V–

50pF

220pF

3kΩ

16

15

14

13

5

6

7

12

11

V+

10

8

9

50pF

SSM2018

100kΩ

18kΩ

18kΩ