Transistor BFY90 replacement / equivalent

[Wawavoun]

Hello there,

In the following circuit I replace the BFY90 by a 2N2222.

The highest frequency come from the shift register LS165 and is 16 MHz.

Will the assembly work with same performances with this change ?
With the datasheets I think yes but I am unsure.
I have no measurement system at such frequency. My scope is 20 Mhz bandwith so it show nothing serious at 16 MHz.

Thanks for help and explanations.

Regards.
Philippe

[Kleinstein]

The BFY90 is quite a bit faster and lower capacitance than the 2n2222. So it would be a bit slower. The input side looks like is is reasonable low impedance, so it may still work, but it depends on what the ouput is used for.

[Wawavoun]

The output feed the composite video input of lcd tv.

Today the tv (which works well with similar others systems) dont show anything.

All the board is new and debugging is on the way but far from finished so I do not incriminate the 2N2222 at this moment.

[Kleinstein]

Composite video should be OK, as the frequency is limited (AFAIR some 6 MHz). So a slightly slower transistor should not be a problem.

[edavid]

A 20MHz scope is fine for debugging this.  If the SR is clocked at 16MHz, the maximum output frequency is 8MHz.