cunning current source 01 PUBLIC

This produces a voltage follower which has an output
that has a current limited pullup of IUP and a pull down
of IDN.

Simulate > Time Domain > Run Time-Domain Simulation

This produces a voltage follower which has an output that has a current limited pullup of IUP and a pull down of IDN.

This version has no output voltage limits.

This is otherwise known as a "Cunning Current Source".

The current from I1 is given by the expression:

0.5((IDN+IUP)TANH((V(N2)-V(N1))*1k)+(IDN-IUP))

where in this example:

IDN = 10mA IUP = 20mA

Sadly, CL gets the "Sweep Parameter" option horribly wrong so you'll have to try different values of Rload manually to see what happens.

Try varying Cload, IUP and IDN too.

Some interesting special cases are:

1) IDN = 0 and Rload is very large or open circuit (1G).

Then the circuit turns into a precision peak detector.

2) IUP = 0 and Rload is very large or open circuit (1G).

Then the circuit turns into a precision trough detector.

3) IDN = 0 with a finite IUP and swept load resistance will show that the source behaves like a current limited positive output bench PSU: it will source current but not sink it.

Setting IUP = 0 with a finite IDN creates a current limited negative supply. (See cunning current source 02:

https://www.circuitlab.com/circuit/tuf78c/cunning-current-source-02/)

Simulate > Time Domain > Run Time-Domain Simulation

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