# Modeling a PNP circuit in LTspice, is this a short?

#### Yami

Joined Jan 18, 2016
343
Hi guys,
I was just messing about modeling a PNP circuit in LTspice. I made a mistake with the first circuit where I connected the second voltage supply directly to ground. I measured the current through the voltage source and the plot shows the result. Isn't the voltage source connected directly to ground? Shouldn't it show a dead short/infinite current draw?
The correct circuit is on the right.
Thanks in advance for the help.

#### Papabravo

Joined Feb 24, 2006
16,473
The minus side of the voltage source is actually at -5VDC. the other side of R1 is at 11.3 VDC or about 0.7 VDC below the 12 Volt Supply. So it pulls about 65 mA, just like the simulation says.

#### crutschow

Joined Mar 14, 2008
27,402
Isn't the voltage source connected directly to ground? Shouldn't it show a dead short/infinite current draw?
One side of the source is connected to ground, which is not unusual.
Both sides would need to be connected to ground for an infinite-current short.

#### Yami

Joined Jan 18, 2016
343
Thanks everyone, this raises another question for me. Where would the circuit shown on the left be used in a real life application? In other words does the circuit on the left make any sense to be used?

Again thanks

#### Papabravo

Joined Feb 24, 2006
16,473
I don't know off the top of my head, but it doesn't seem worth the effort to contemplate.

#### crutschow

Joined Mar 14, 2008
27,402
In other words does the circuit on the left make any sense to be used?
Not with those voltage levels and base resistor value.
It would work as a high-side switch if V1 switched between ground and V2, and R1 is about 10 times the value of R2.