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Commodity IC Data: LM3900 Transresistance Amplifier
Q: I have noticed that not all the op amps offered commercially by companies such as National Semiconductor or Harris (now Intersil) are normal. What exactly is a Norton amplifier good for? And, also, why would I ever want to use a transconductance amplifier such as the LM13600/LM13700, or the older CA3080?
A: These components are indeed commodity ICs in that they are low in cost and are readily available. These particular parts are not voltage-in, voltage-out op amps, and they are usually not best applied where voltage amplifiers are able to be used. Most familiar op-amp circuits are best implemented with voltage-amplifying op amps or, for fast applications, with current-feedback op amps which, conceptually, have both voltage and current inputs.
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