Constant gm filter design

[whitewiz]

I need to design constant gm filter to put it in front of preamplifier in order to get

constant gain at the 100MHz frequency. Unfortunately, there is no good textbook in

the library. It is so appreciated if you recommend any publications or books relating

to constant gm filter design.

Thank you

Chris

 

[LvW]

Please, can you explain your requirements in more detail ?
Normally, gm-C filters are used because of their gm tuning capabilities; but for which purpose do you require "constant gm" ? Or do you generally mean "constant gain" ?

 

[whitewiz]

Please, can you explain your requirements in more detail ?
Normally, gm-C filters are used because of their gm tuning capabilities; but for which purpose do you require "constant gm" ? Or do you generally mean "constant gain" ?

I think constant gm filter can help preamplifier to get constant gain.

When I measured the output performance using oscilloscope and function generator,

100MHz square wave pulsed can not be amplified. Output looks like sinusoidal wave.

Therefore, the wide bandwidth is required. Without constant gain, only sinusoidal wave can be amplified.

Please let me know there is any good way to make constant gm or constant gain filter.

Thank you for your reply

 

[LvW]

I think constant gm filter can help preamplifier to get constant gain.
When I measured the output performance using oscilloscope and function generator,
100MHz square wave pulsed can not be amplified. Output looks like sinusoidal wave.
Therefore, the wide bandwidth is required. Without constant gain, only sinusoidal wave can be amplified.
Please let me know there is any good way to make constant gm or constant gain filter.
Thank you for your reply

I really don´t understand the problem: Without constant gain, only sinusoidal wave can be amplified.
What does this mean ?

 

[whitewiz]

When I tested the input signal with a rectangular shape and 100MHz bandwidth for preamplifier(center freq : 100Mz, bandwidth : 30MHz), the output signal is sinusoidal waveform to be amplified(The shape is supposed to be rectangular). My friend mentioned, your bandwidth of the preamplifier is not enough to amplify the input signal with 100MHz bandwidth and your preamplifier's bandwidth is around 30MHz.

He recommended, you had better design the lowpass or highpass constant gm filter(or the filter with a constant gm or constant gain) and put it in front of preamplifier. I don't think this is the constant resistant filter.

It is so appreciated if I need to design this kind of filter and there is any good material to cover.

I think constant gm filter can help preamplifier to get constant gain.
When I measured the output performance using oscilloscope and function generator,
100MHz square wave pulsed can not be amplified. Output looks like sinusoidal wave.
Therefore, the wide bandwidth is required. Without constant gain, only sinusoidal wave can be amplified.
Please let me know there is any good way to make constant gm or constant gain filter.
Thank you for your reply

I really don´t understand the problem: Without constant gain, only sinusoidal wave can be amplified.
What does this mean ?

 

[LvW]

When I tested the input signal with a rectangular shape and 100MHz bandwidth for preamplifier(center freq : 100Mz, bandwidth : 30MHz), the output signal is sinusoidal waveform to be amplified(The shape is supposed to be rectangular). My friend mentioned, your bandwidth of the preamplifier is not enough to amplify the input signal with 100MHz bandwidth and your preamplifier's bandwidth is around 30MHz.
He recommended, you had better design the lowpass or highpass constant gm filter(or the filter with a constant gm or constant gain) and put it in front of preamplifier. I don't think this is the constant resistant filter.
I

When your signal needs 100 MHz bandwidth - and your amplifier has only 30 MHz,
I don´t know how a filter could help. Or did I misunderstand something ?
Perhaps your friend was joking ?

 

[whitewiz]

From your answer, the filter can not help the preamplifier to get output with this kind of specification. Is that right ? I am also confused about the concept so I am asking the question here.

I guess the bandwidth of the Ultra wide band amplifier is 2 or 3 times bigger than center frequency. I think I need to design the filter with broadband matching and constant gain in the frequency domain like ultrawide band amplifier.

Thank you for your answer

Chris

When I tested the input signal with a rectangular shape and 100MHz bandwidth for preamplifier(center freq : 100Mz, bandwidth : 30MHz), the output signal is sinusoidal waveform to be amplified(The shape is supposed to be rectangular). My friend mentioned, your bandwidth of the preamplifier is not enough to amplify the input signal with 100MHz bandwidth and your preamplifier's bandwidth is around 30MHz.
He recommended, you had better design the lowpass or highpass constant gm filter(or the filter with a constant gm or constant gain) and put it in front of preamplifier. I don't think this is the constant resistant filter.
I

When your signal needs 100 MHz bandwidth - and your amplifier has only 30 MHz,
I don´t know how a filter could help. Or did I misunderstand something ?
Perhaps your friend was joking ?