I am trying to generate a sine wave signal. I am following this guide http://www.ti.com/lit/ml/sloa087/sloa087.pdf from TI. The thing is I cannot find the IC that they are using (TLV2471) and I only have OPA604 and LM3900 op-amp and the circuit doesn't work. I have tried the Wien Bridge from page 12 and phase shift oscillator from page 17.
For the Wien Bridge circuit, the OPA604 give very small amplitude sine wave (from about 2.3 to 2.7V) and the frequency reading in my oscilloscope jungling around from 50kHz to 40Mhz. the LM3900 give a nearly square wave at about 5kHz.
For the phase shift oscillator circuit, the OPA604 gives a similar small sine wave with jumping frequency while the LM3900 gives no oscillation, the ouput just stay at about 2.5V.
So could anyone please help. Any pointing is also greatly appreciated.
Best Answer
Your OPA604 needs at least a 9v supply and even then it doesn't have the 'rail-to-rail' outputs of the TLV2471.
Your circuit might still work work this opamp if you increase the supply voltage though.
The LM3900 is not a 'normal' opamp. Its a Norton type which works on the currents into/out of its inputs and not the voltages on them.
This one will never work in that circuit.