MITSUMI
Compander IC MM1077
About Application Circuits
1. Mike amp
The compressor unit mike amp is exposed to circuits outside the IC via positive and negative input pins.
The positive input pin is connected to C.Vref by a bias resistance of 100kΩ, so that no external bias is
needed.
When pin 4 is open the gain is lowest, and an input voltage of approx. 13.5Vrms is the reference level.
When the external resistance is 0Ω, the gain is maximum. The internal configuration appears in Fig. 1.
2. Rectifier circuit unit (rectifier)
The product of the external capacitance and the internal resistance (10kΩ) determines the time constants
for the attack and release times.
3. Compressor amp
The compressor amp requires that the DC gain be unity and the AC gain be infinite. In order to satisfy this
requirement, AC feedback is eliminated and only DC feedback is used. In order that only DC feedback be
present, a capacitor to eliminate AC components is connected to pin 8. The cutoff frequency is determined
by the product with the internal resistance (100kΩ).