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Author Topic: Transistor Graphing Device  (Read 782 times)
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It depends on the op-amps, I am sure that these, like most, require a split supply*. I don't know what you mean by "top right" but the input at the *top left* is stated to be +/- 10 V meaning that the circuit can sink and source current.

A positive rail only supply would only be able to source current.
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Here's a circuit than sources current (a bit harder than a programmable sink)
http://www.seekic.com/circuit_diagram/Power_Supply_Circuit/VOLTAGE_PROGRAMMABLE_CURRENT_SOURCE.html

I don't understand strange symbol in top right of the picture. It shows +-10V Gnd, but there are no +/-10V rails in the rest of the circuit. Does this circuit require positive and negative voltage power supply?

There's a voltage source representing the input at the top left, perhaps that what you mean?   The load
is represented by a programmed (dependent) current source symbol bottom right.  No supplies are shown
in the circuit, they are implicit (normally the case for signal processing schematics, supplies are boring
detail).
(for instance look at the datasheets for the amplifiers referred to)
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thanks, you are right, it was "top left".
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Yeah, nice and simple circuit, but I do not have power supply with -10V.

Additionally, even if I had supply with -10V, can I damage oscilloscope? Where is my ground?
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Lacey, Washington, USA
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If you only want to source current with it, then you would only be supplying a 0 to +10V signal to it, and could then use just a +15V power supply. But it will limit how linear it is down at very low voltages at the output, and at low currents.

When only sourcing current, as you'd need for a transistor curve tracer that only does NPN or N-Channel MOSFET, you could use a lower voltage, low current supply for the - supply. It could be generated with a charge pump, or a small switching regulator like the MC34063 can be wired up to generate a regulated - voltage.

If you are getting into analog, you should have a variable power supply with tracking or separately adjustable + and - outputs. 15V is about the max you'll probably need.
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Steve Greenfield AE7HD
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Lacey, Washington, USA
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I should mention, the maximum current that circuit can source or sink is limited by A1.
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Steve Greenfield AE7HD
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