peak-to-peak value of output in buffer circuit decrease,why?

in simulating of buffer circuit, i found that the peak-to-peak value of the output is lower than that of the input, can anyone tell me the reason, and this will affect the performance of the buffer?

thanks.

Re: peak-to-peak value of output in buffer circuit decrease,

can you please post your buffer circuit...

one main thing is the output of the buffer will be equal to the input only when the gain is 1 and there could be some resistances and voltage drops in your circuit that could be preventing this from happening....

Re: peak-to-peak value of output in buffer circuit decrease,

flysnows said:

in simulating of buffer circuit, i found that the peak-to-peak value of the output is lower than that of the input, can anyone tell me the reason, and this will affect the performance of the buffer?

thanks.

Click to expand...

I think there are some problems in it.

I dont know your testbench or circuit.

however, you should check the dynamic

performance and other specs of it.

Is it a rail to rail input/output buffer?
If not, there are finite input/output voltage ranges.

maybe your circuit dc point has sth. wrong when you send input signal, check the transistor work condition.

Re: peak-to-peak value of output in buffer circuit decrease,

When u have connected ur opamp in the unity configuration which creates as a buffer and when you put in transient signal at the positive terminal and checkout the output signal at the output, either you should be getting the output swing almost same amplitude as the input swing or just a bit less. If your output signal is far lesser than the input signal, then most probably your opamp slew rate is very low, which limits the output signal amplitude compared to input. You can confirm this by injecting a transient signal at the input with a lower speed, let say 100Mbps and see the output amplitide. So, if you can see that ur output amplitude is same as the input swing at lower speed, that will confirm the slew rate is a issue. You can improve the slew rate of your opamp by incerasing the dc biasing current or reduce the load capacitance. Pls check some of your analog design book on how to improve the slew rate.

Re: peak-to-peak value of output in buffer circuit decrease,

flysnows said:

in simulating of buffer circuit, i found that the peak-to-peak value of the output is lower than that of the input, can anyone tell me the reason, and this will affect the performance of the buffer?

thanks.

Click to expand...

if your input is rail to rail, you cannot get the output same as input eventhough as a buffer unless ur opamp is rail to rail opamp.

Re: peak-to-peak value of output in buffer circuit decrease,

I think there are two possibilities.

First, your input or ouput is not rail to rail.

Second, your open loop gain is not large enough, which reduces the closed loop gain and causes error @ output. For more information, please visit the following website.
http://www.maxim-ic.com.cn/appnotes.cfm/an_pk/1094