Designing a buffer connected to the output node of preamplifier.

[paraon00]

Hi, ^^
I want to design a buffer connected to the output node of preamplifier.

The output signal of preamplifier is influenced by capacitive load,
and I want to probe the output signal of preamplifier. Therefore, buffer is necessary.

1. Small input capacitance of the buffer is hoped(<100fF).
2. Load capacitance of the buffer may be 20pF(including PAD and oscilloscope).
Therefore, buffer has to have a large driving capability because the speed of
preamplifier is over 1MHz.

How do I design this buffer?

thank you, all.

 

[MikeR]

buffer design

which technology you use?
about output stages you can read in:
1) Johan Huijsing - operational amplifiers theory and design
2) Johan Huijsing - Desing of Low-Voltage Low-Power Operational Amplifier Cells

 

[VSMVDD]

Re: buffer design

Hi

you should use a fixed referance gain block of a known design

if your a student you should ask your tutor

or show initiative and source your own

:arrow::idea:

 

[wonbef]

buffer design

single-ende output or differetial-ended output? if it is a single-ended output, there are some circuits for high speed applications.

 

[careking]

buffer design

hi, generally, a two stage amplifier with a follower output stage maybe meet your require, but it will need a power dissipation about 100uA, and in order to save the area and keep a good phase margin, you had better make a good compensation for the zero point. Further more,
incording to the value of input signal, you can choose the proper input transistors.

 

[surianova]

Re: buffer design

Hi, ^^
I want to design a buffer connected to the output node of preamplifier.

The output signal of preamplifier is influenced by capacitive load,
and I want to probe the output signal of preamplifier. Therefore, buffer is necessary.

1. Small input capacitance of the buffer is hoped(<100fF).
2. Load capacitance of the buffer may be 20pF(including PAD and oscilloscope).
Therefore, buffer has to have a large driving capability because the speed of
preamplifier is over 1MHz.

How do I design this buffer?

thank you, all.

I think it is better to use folded cascode as a buffer... and also this opamp has high gain and is more stable with higher capacitive load and also it has only one pole. But make sure the opamp still can acheive BM 1Mhz with 20 pf load.

 

[rajharvijay]

Re: buffer design

How can you use folded cascode as a buffer??