Transistor characteristic curve problem

Thread Starter

Vihaan@123

Joined Oct 7, 2025
220
1771411065060.png
1771411645272.png

The base Current is assuming currents into the transistor
\[ I_B = \frac{-9V + 0.7V}{30000 Ohm} \\
I_B = -0.27mA \\
\]
I am assuming the transistor in saturation from IB = -0.27 mA the collector current as per curves is -37mA and i assume this is the maximum value of the collector current.
\[
Ic = (-9V + 0.2V )/ 1000 Ohm = -8.8mA \\

V_{BE} = -0.7V; \\
V_{CE} = -0.2V; \\
V_{BC} = V_{BE} - V_{CE} = -0.7V + 0.2V = -0.5V \\
V_{CB} = 0.5V
\]
For pnp transistor a positive value of V_CB means it is forward biased. Hence it is in saturation.
Little bit of struggle for pnp transistor with sign convention and hopefully it is correct and (i assume i cannot verify my answer).
Few questions i have is the VCE value is it possible to take even a lesser value?
And for example, if it is -0.1V of VCE it does not intersect the IB current and hence the value of VCE of -0.1V is not valid, am i correct and what does it mean if it is not intersecting?
 

Thread Starter

Vihaan@123

Joined Oct 7, 2025
220
Hi V123
Note it states the transistor is a germanium type check your Vbe
E
Can i take it as standard -0.3V or as per the text book for the input characteristics
1771425598812.png
and based on the values of IB = -0.27mA and VCE = -0.2V the VBE voltage will be -0.22V approximately should be considered?
 

schmitt trigger

Joined Jul 12, 2010
2,027
As long as you clearly state your assumed Vbe voltage in your calculations, you should be fine.
After all, the homework’s purpose is to demonstrate that you understand the process to calculate the operating point.
 

MrChips

Joined Oct 2, 2009
34,628
Don't overthink the problem. Whether the base-emitter voltage is 0 V or 0.3 V is not going to make any difference in the calculation.

Max base-emitter current is -9 V / 30 kΩ = -0.3 mA
Max collector current is -9 V / 1 kΩ = -9 mA

Draw the load line between Ic = -9 mA, Vce = 0 V and Ic = 0 mA, Vce = -9 V
 
Top