archiees
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hi,
I am designing a transimpedance amplifier which needs to amplify around 100pA of current to few mVs , the signal frequency is from 10Khz to 10 Mhz. I start with a 1M ohm resistor to convert this current into voltage and use a FET in a source follower configuration for pre-amplification.
My problem is the high impedance input signal source. I model it as a current source in parallel with a 20pF capacitance.
This 20 pF capacitance with the input resistor of 1Mohm forms a high frequency pole - severely limitting my BW to less than 50 KHz.
I don't want to reduce my 1M resistor which will reduce my Transimpedance gain. As my signal before being fed to the preamplifier should be higher than the signal noise floor.
So, i am stuck and i don't know how to keep the sufficient gain upto 10MHz. Please help.
I am designing a transimpedance amplifier which needs to amplify around 100pA of current to few mVs , the signal frequency is from 10Khz to 10 Mhz. I start with a 1M ohm resistor to convert this current into voltage and use a FET in a source follower configuration for pre-amplification.
My problem is the high impedance input signal source. I model it as a current source in parallel with a 20pF capacitance.
This 20 pF capacitance with the input resistor of 1Mohm forms a high frequency pole - severely limitting my BW to less than 50 KHz.
I don't want to reduce my 1M resistor which will reduce my Transimpedance gain. As my signal before being fed to the preamplifier should be higher than the signal noise floor.
So, i am stuck and i don't know how to keep the sufficient gain upto 10MHz. Please help.