I have a circuit in which a square wave with smaller amplitude should be amplified with an opamp. Before, I used a MAX492 which has G/B-product of 500 kHz. With this circuit I manage to easily amplify the signal, Vcc is single supply 3.3V:
This gives me a nice amplification of around 5 (1 + 40k/10k) and the input is very high impedance.
Now here's my problem: I bought some LF356 Opamps with GBP of 5Mhz and tried to put it in instead of the MAX492. However, I noticed that
- it doesn't seem to work below 5V at all
- it pulls up the positive input to some DC voltage, overlaying the signal if I don't use a decoupling cap.
Is this how this old opamp is supposed to operate? Is this because I'm using a single supply?