Comments on Choosing between common-drain JFET amplifier, and common-source

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Choosing between common-drain JFET amplifier, and common-source

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Do common-source JFET amplifiers have an advantage over common-drain? The JFET would be in a low noise photodiode amplifier. The signal is 100us pulses with 10us raise times.

Here are the schematics which I have in mind.
The op-amp would be LTC6252 or LT6200. Single-supply operation is desirable for me.

Common-drain

Schematic snippet. Common-drain photodiode amplifier consisting of a JFET and and operational amplifier. I picked up this common-drain idea from the LT6200 datasheet (application example on the first page).

Common-drain JFET has a prototyping appeal, because it would be easy to try a simple transimpedance op-amp (without a JFET) on the same PCB. Fallback position.

Common-source

Schematic snippet. Common-source photodiode amplifier consisting of a JFET and and operational amplifier. I picked up this common-source idea from this app note.

JFET photodiode

posted about 3 years ago

CC BY-NC-SA 4.0

3y ago

misk94555‭

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Compound transimpedance amplifier (1 comment)

Links not to datasheets (1 comment)

Nick Alexeev‭ wrote 6 days ago

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The goal of this JFET circuit is to have a fast op-amp with low input bias current. Another way to achieve the same goal is to use compound (TIA). The first op-amp is chosen for low input bias current and low noise. It could be a FET op-amp. The second op-amp is chosen for high bandwidth. It could be a bipolar op-amp. Details about compound TIA here https://www.edn.com/edn-access-05-22-97-embedded-gain-supercharges-fet-transimpedance-amplifier (by Michael Steffes, EDN, 1997)

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Comments on Choosing between common-drain JFET amplifier, and common-source

Choosing between common-drain JFET amplifier, and common-source

Common-drain

Common-source

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