Gain Bandwidth Product Approximation per Datasheet? Off by 10x

Thread Starter

imzack

Joined Nov 3, 2010
71
Hi,

I am using a 2N3904 BJT, and according to the datasheet, there is a Gain Bandwidth Product min of 300MHz.

When I test this in LTSPICE, it appears according to the sim, that Gain BW Product is more like 3GHz.


What would typically cause a 10x difference of these values? Is there a way to better approximate a Gain BW Product by hand / without LTSPICE?

Thanks!
 

SLK001

Joined Nov 29, 2011
1,541
What would typically cause a 10x difference of these values? Is there a way to better approximate a Gain BW Product by hand / without LTSPICE?
Errors can be caused by:
1) Operator error
2) Poor implementation of model.
3) Bad software
4) Bad circuit for test.

By hand you'll need a signal generator and some way to measure the amplitude of the output of your test circuit, ie, oscilloscope or spectrum analyzer. Measure gain at 10 MHz and 100 MHz, then draw a line from these two amps to a point (frequency) where the gain is 0dB.
 

Thread Starter

imzack

Joined Nov 3, 2010
71
Sorry to use the "by hand" term. I am wanting to stick with datasheet and modeling right now.

I need to mabye fix my model then? To try to get the Gain Bandwidth product to match my datasheet.


How does the gain bandwidth product vary by part to part? Are you familar?

Is there a way in LTSpice to set the Gain BW of a part manually?

Thanks
 
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