Happy Thanksgiving All:

I have a question regarding transistors and frequency in general. Let's say you have a small signal 2NXXXX transistor, and it is rated for 1.5Mhz max.

If the signal amplitude applied to an amplifier or switching circuit were small signal,and the frequency surpassed it's rating, would the transistor burn out or just attenuate the signal and cease working until the F is reduced?

Okay... now what if it were fed into a high powered transistor such as a T03 packaged device?

Just Curious about what would happen. I don't have a signal generator that goes high enough to do the experiment.

Aram

 

Happy Thanksgiving All:

I have a question regarding transistors and frequency in general. Let's say you have a small signal 2NXXXX transistor, and it is rated for 1.5Mhz max.

If the signal amplitude applied to an amplifier or switching circuit were small signal,and the frequency surpassed it's rating, would the transistor burn out or just attenuate the signal and cease working until the F is reduced?

Okay... now what if it were fed into a high powered transistor such as a T03 packaged device?

Just Curious about what would happen. I don't have a signal generator that goes high enough to do the experiment.

Aram

The output fails to follow the input.

 

At the Transition Frequency, fT or the Gain-bandwidth product frequency the hfe (AC current gain) is 1. Above it the hfe is less than 1.

 

With no damage at low signal levels I suppose.. Correct?

Aram

 

A transistor does not suffer damage from signals that are beyond its frequency capability.

It simply does not respond to them. In fact its response degrades progressively as frequency increases until it posesses no response at the transition frequency.

There is a situation where a transistor can destroy itself by (high frequency) oscillation if it is incorrectly configured. However this frequency is still within the transistor's operating range, just usually outside the range of signal frequency of interest.

 

To assist you with your question, I am quoting the following:

"If the GBWP of an op-amp is 1 MHz, it means that the gain of the device falls to unity at 1 MHz. Hence, when the device is wired for unity gain, it will work up to 1 MHz (GBW product = gain x bandwidth, therefore if BW = 1 MHz, gain = 1) without excessively distorting the signal. The same device when wired for a gain of 10 will work only up to 100 kHz, in accordance with the GBW product formula. Further, if the minimum frequency of operation is 1 Hz, then the maximum gain that can be extracted from the device is 1 x 106".

This information can be found at:
http://en.wikipedia.org/wiki/Gain-bandwidth_product