Hi,
I tested an Gain-programmable circuit which uses IC - PGA112. The circuit is shown as below:
The input signal is connected to C174 then into CH1. The amplified output can be measured at Min2 or RLine1. Its gain is controlled by SPI.
PGA112 has binary gain (6db step). As a testing result, it shows correct gain at low-gain-setting for Gain = 1, 2, 4, 8,16. However, when the set gain is high (Gain = 32, 64, 128), the output gain doesn't has enough gain as its spec. It should has 6db gain increased when the gain setting step-up, However, as a result, it only showed about 2-4db gain up for the high-gain setting.
What may be wrong with this circuit or chip? Any special care needs for this IC ?
Regards,
Jun