CIRCUIT DESCRIPTION
The GP520A is a programmable analog signal path IC designed for use in hearing instruments. The GP520A’s programmable parameters are adjusted by external programming currents, such as generated by the GP521. The GP520A provides a 2.5 µA reference current for use by the GP521. Sixteen settings are possible in the GP521, allowing the Programmable Current Sink (PCS) to sink between 0 and 1.875 x IREF.

FEATURES
• programmable parameters
    - gain
    - low pass filter
    - high pass filter
    - AGC threshold
    - release time
    - MPO
    - receiver bias voltage
• on-chip voltage regulator
• typical gain 60 dB
• voltage drive output stage
• telecoil preamp