Hi,
I want to know what will the value of the "V4" that keeps the difference bewtween the inverting and non inverting inputs zero.
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jess
- posted
10 years ago
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- Vote on answer
- posted
10 years ago
-- Vin + Vbe(Q1)
- Vote on answer
- posted
10 years ago
Not sure what node you are referring to, so I will assume it is #4 which is the op-amp output node. Transistors have an average band gap of ~650mV at room temperature and it should be 650 mV more than what is at the emitter.
With that, you should be able to construct the rest. Good luck with your home work.
Jamie
- Vote on answer
- posted
10 years ago
Its basically a voltage follower developing a fixed voltage across the current sense resistor, that voltage is within Voffset of the op-amp minus the forward bias drop in the BE junction.
The fixed voltage developed across the fixed resistor forces a predictable current to flow - this current (minus the transistor's base current) also flows through the collector load resistor.
- Vote on answer
- posted
10 years ago
Its basically a voltage follower developing a fixed voltage across the current sense resistor, that voltage is within Voffset of the op-amp minus the forward bias drop in the BE junction.
The fixed voltage developed across the fixed resistor forces a predictable current to flow - this current (minus the transistor's base current) also flows through the collector load resistor.