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

Thread Starter

Yami

Joined Jan 18, 2016
290
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.
PNP circuit.jpg
 

Papabravo

Joined Feb 24, 2006
13,926
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
25,120
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.
 

Thread Starter

Yami

Joined Jan 18, 2016
290
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 :)
 

crutschow

Joined Mar 14, 2008
25,120
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.
 
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