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Re: Low Noise Transistors: ZTX851 versus ZTX689B Noise Performance

Posted: Wed Nov 20, 2019 5:48 pm
by mediatechnology
Wow. My guestimate of 5.5 was pretty close.

The ZTX689 may be better overall as a mic preamp simply due to its higher gain (lower Ibias) and lower Cob.

Thank you Bill and Hans!

Re: Low Noise Transistors: ZTX851 versus ZTX689B Noise Performance

Posted: Mon Jun 29, 2020 3:32 pm
by al2002
Is any rbb data available for the pnp ZTX 789? Also, has anyone measured the hfe variations for a batch of 689/789s? Would be useful to know.

Thanks in advance.

Re: Low Noise Transistors: ZTX851 versus ZTX689B Noise Performance

Posted: Thu Jul 02, 2020 3:42 pm
by mediatechnology
I would have to work backwards from the noise measurements but the rbb' of the ZTX789 is between the 5Ω rbb' of the ZTX689 and the 2SB737's 2Ω rbb'.

I don't have enough ZTX789 to get a meaningful hFE spread.