[Amps] Need Zener for 2KD-3

[Al Kozakiewicz]

Just FYI, this circuit is called an emitter follower.  Back in the early 70's, this was the "regulated" power supply of choice when I worked in a lab - a 5 or 12 V Zener diode, depending on the application,  a 2N3055 transistor and a suitable resistor.  As you should expect from a 3 component regulator, the regulation sucked and the power dissipated by the transistor could be significant if you were trying to drop too much voltage.

Once modular supplies became cost effective we used them instead.  Our job was to design custom systems for a specific purpose, not design the power supplies for them!

Al
AB2ZY
________________________________________
From: Amps <amps-bounces at contesting.com> on behalf of Manfred Mornhinweg <manfred at ludens.cl>
Sent: Tuesday, February 3, 2015 8:36 AM
To: amps at contesting.com
Subject: Re: [Amps] Need Zener for 2KD-3

My way to replace power zeners is to use a common low power zener together with
a power transistor and a small resistor. The zener goes collector to base, the
resistor base to emitter. The transistor is selected to comfortably handle the
voltage, current and power, the zener is a low power unit (typically either 1
watt or 0.4 watt) with a voltage 0.6V lower than the original power zener, and
the resistor's value is chosen to bias the small zener to about 10% of its
maximum current, with 0.6V across the resistor.