Iam using a vibration analyzer or sensor.I need to amplify the above sensor's output signal.For this purpose i used opamp ic 741 in the non inverting configuration.But when i gave the input to the amplifier from a function generator the amplifier gave a gain of about 50 and 68 initially.When i changed the input frequency from the function generation to 1 khz amplifier gave a gain of 100 even though the amplifier circuit was originally designed to give a gain of about 101.
But for my application,when i give the input to the amplifier from the output of the vibration analyzer the gain of the amplifier circuit changes to a huge value of about 450.
What may be the reason for this?
At first i used AD620 ic for the amplification instead of the op-amp ic 741.The behaviour of the gain at that time was also similar to now.
Please, post the circuit you have implemented and the sensor you are using.
However take into account that 741 has a gain bandwitdh product of about (or less than) 1MHz, then the maximum frequency you can amplify with gain=100 is roughly 10 kHz.
AD620 can have gain=100 with signals up to 120 kHz.