[time-nuts] Suggested Low Noise Transistors

johncroos johncroos at aol.com
Sun Jul 26 10:15:24 EDT 2015


I offer the following for your consideration.
Once upon a time - about 1968 Motorola introduced
4 low noise transistors for audio and low frequency 
applications. There were th 2N5086, 5087, 5088 and
5089. 

The 5086 and 5087 are PNP and the 5088 and 5089
are NPN. They are almost perfect complements to each other.
They are still made though the part numbers
are now MMBT2N5088L and so on. As of September 2014 I 
bought and used several of them in a photo transistor preamp for
a laser theodolite receiver. They are commonly available from
distributor stock.

They differ slightly in noise figure and Beta. Since 1970
I have used
them in a number of professional applications from DC up
to 50 MHz. The latter a 6 channel summing amplifier for
a military mapping photo transistor device.

These are some of the hottest bi-polar devices
known with a specified minimum beta of 150 at 100 uA. 
The beta is pretty flat up to 10 mA. The current gain
bandwidth product  varies from a bit less than 50 
at 100 uA up to  500 at 10 mA. At 1 mA it is 200.

The low frequency noise figure IS specified - 

2N5086 3.0 dB MAX (Ic = 20 uA, Vce = 5 v, Rs = 10 K, from 10 Hz to 15.7 kHz)

2N5087 2.0 dB Max, 1.0 dB typical(Ic = 100 uA, Vce = 5V, Rs = 3K, f = 1.0 kHz)

Data is provided for the effect of source resistance and Ic on the
noise figure.

Data for the complementary 2N5088 and 2N5089 is nearly 
identical. You can look it up. It is all on the data sheet for
the original devices and may be found in the "Semiconductor Data
Handbook" issued my Motorola in the 1970. the data may also be
on the "ON" semiconductor web site among other places.


With their relatively low high frequency
response (as compared to a 2n2857) you are not risking
oscillations up in the the microwave bands where most of you
do not have the test gear to find and fix any funny business.
 
This is a really nice calm set of devices and easy to use.
I believe that when I bought them last year 
they were around a buck each.

The 5086 and 5087 are PNP and the 5088 and 5089
are NPN. They are still made though the part numbers
are now MMBT2N5088L and so on. As of September 2014 I bought and used several of them in a photo transistor preamp for
a laser theodolite receiver. They are commonly available from
distributor stock.

I have not applied them in low noise oscillator applications
and have no idea as to their suitability for that. But they
are one hell of a transistor family and worth knowing  about.

Best regards       john c roos   K6iql  spring hill ks




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