# Simulating a specific circuit on LTspice  Because I wanted to find the Voc and the Isc (of the load) for the circuit to calculate Rth, I decided to put the resistance as 99999999 to find Voc, and then 0 to find Isc.

The problem here is I have no idea how to edit the current controlled voltage source to reflect current passing through the resistor. The Youtube tutorials I found online only teach the methods to connect the CCVS to a current source, but not to a resistor.

I tried to put the Value of the dependent source as R1 and Value2 as 3 but LTspice tells me that R1 is an unknown value.

The problem here is I have no idea how to edit the current controlled voltage source to reflect current passing through the resistor.

To begin with, you need a current dependent current source and not a current dependent voltage source. Or you can choose an arbitrary source.

Your input to the source is ill-defined by "R1". See how this example works: - You need a dependant current source (B1 above or H for a CDCS) and the variable that is your input is I(R1): - As you should be able to see, Vin (left) is going to be 1 volt and Vout (right) is going to be 10 volts.

Spice only allows measuring current through voltage sources. So instead of specifying R1 as the current-controlling device, specify V1 instead. The current is the same through both components anyway. If you ever find yourself in need of a current through a device that is not a voltage source, just add a voltage source of 0V in series. This is also the "official" method suggested by the people that created Spice 3f5 (the precursor LTspice).

zero valued voltage sources may be inserted into the circuit for the purpose of measuring current

• Many thanks, Sven and Andy. I have another question, however. What if I need the potential difference of a resistor for a voltage dependent voltage source? – John Galt Jan 15 '18 at 14:17
• Then you can use a voltage controlled source, which is a 4 terminal device. Ie. you can connect the controlling voltages. Glad to help! – Sven B Jan 15 '18 at 15:20