Multistage Opamp design 100KHz

Thread Starter


Joined Oct 27, 2015
Based on my previous Thread, (Multistage Operational Amplifiers with gain and offset)

I have to redesign my project for another Project for recording animals.
first many thanks to all the researchers, professionals, tinkerers and hobbyists, for sharing your experience in creating a robust reliable design.
thanks for pointing things out with the 50Ohm load and the current usage for the signals, alternatives, solutions and solving misconceptions I had in mind. also thanks for pointing out that the butterworth acts as a buffer stage :) That would have taken me ages:).

I have a general understanding but I lack some experience in building these concepts.
I am always sceptic as in why how things are done and how they can be justified, by asking why and how?.

so Ill start from the beginning:

now for an other project I would like to the same: amplify a signal 0.15V to 5V variable gain, and with a variable bias.
the design for a filter is based on Texas Instruments Webench designer and includes a low pass filter till 100KHz all fine all good.

The questions are:
can I use the same OPA827A for amplification from 0.15 till 5V? or do I need a other amplifier for this.
should I also use the same OPA827A for bias offset? because some output buffers out there have an even higher Slew rate.
should I use the 2n2905 and the 2n2222 for the output buffer to another device with a 50 Ohm Load, is there a good alternative, for those high frequencies 100KHz? LH0002 didnt pop up on digikey.

should I use SMA to BNC connectors? (i didnt made and experience with those yet, beside that they are golden which always looks nice:)(beryllium coated?).

due to the fact of low power LTC3265, I have to redesign the power supply I would like to use the following compact AC to DC convertor at digikey. Still this one has a 120mV/PP ripple on it, what is a good circuit to filter these signals because High frequent noise from AC/DC on common mode isnt fun, I have seen some applications on EMI filtering but they are used for filtering DC from batteries to supplies. which inductors are good against high frequent signals for pcb design at a load of total 200.2mA, help would greatly be appreciated in this. should I use the PI topology or T in parallel for +15 and -15V?

I got a hunch in searching EMIRR signals,

due to the fact these applications are cheap, still a lot of ripple, high frequent noise exists on the DC lines (I have met this experience with the Meanwell family, which have 55KHz and other nasty high frequencies on an other project in which I use Thermocouples T with a dual supply AD595A with filters to create a sleek signal.

Many thanks for taking your time reading and transmitting thoughts and ideas!


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