Hi Tomoaki,
Please ask the customer to use the below circuit for open-loop gain and phase simulation.
I think all the customer has to do is probe the output differentially (VM1). Also, the customer has to select the Amplitude & Phase in the AC characteristic simulation. Here is the TINA-TI simulation for the same: THS4541_OpenLoopGainPhase.TSC
Best Regards,
Rohit
Hi Rohit-san,
Thank you for your reply.
I have a question about this simulation circuit.
Althougth I understand this circuit is standard for open-loop gain and phase simulation, I think that It is different from the actual circuit.
It is feedback resistance and input resistance etc.
I think that conditions such as bias current will change somewhat.
It is different from the actual circuit.
The difference is feedback resistance and input resistance etc.
I think that conditions such as bias current will change somewhat.
Is this effect small enough to ignore it?
They intend to place capacitors for phase compensation at the positions C2, C4 in the figure below.
In order to judge the proper values of C2 and C4, should they verify by adding C2 and C4 to the received open-loop circuit?
Best regards,
Tomoaki
Hi Rohit-san,
Thank you for your reply.
I have a question about this simulation circuit.
Althougth I understand this circuit is standard for open-loop gain and phase simulation, I think that It is different from the actual circuit.
It is feedback resistance and input resistance etc.
I think that conditions such as bias current will change somewhat.
It is different from the actual circuit.
The difference is feedback resistance and input resistance etc.
I think that conditions such as bias current will change somewhat.
Is this effect small enough to ignore it?
They intend to place capacitors for phase compensation at the positions C2, C4 in the figure below
In order to judge the proper values of C2 and C4, should they verify by adding C2 and C4 to the received open-loop circuit?
Best regards,
Tomoaki
Hi Tomoaki-san,
The open loop gain and phase response is independent (or not related) to the feedback resistance and capacitance that would be placed across the feedback paths. Even though you place resistor and capacitor across the feedback paths, the main amplifier small-signal open loop gain/phase response would still stay the same. The 1G H inductor across the feedback path is responsible for maintaining the closed loop DC path across the main amplifier.
I think what the customer wants to simulate for phase compensation is the noise gain along with open-loop gain. The noise gain simulation includes the feedback resistance and capacitance which usually gives a good estimate about the phase compensation required for given input capacitance. You could use the below circuit to simulate the noise gain characteristic for a given feedback circuit. The Noise gain in the below circuit equals 1/VM3. It is important to note that the intersection of the noise gain with the open-loop gain should not be greater than 20dB/decade for stability purposes.
Attached TINA-TI circuit for the same: THS4541_OpenLoop+NoiseGainSim.TSC
Best Regards,
Rohit
