Mini Keying Adapter
01/07/2016
Page 5 of 6
power strips or house circuits, make sure you don’t have a floating ground or a high
resistance path somewhere. It’s not normally an issue, but I’m always surprised at how
we find new ways to break things.
Theory of Operation
In logic terms, the Mini Keying Adapter consists of two inverter/buffer stages.
The gate of MOSFET transistor Q1 is normally held high by resistor R1, keeping Q1
turned ON (conducting). Q1 presents a low resistance to ground, keeping the gate of Q2
near ground potential. In this state Q2 is turned OFF (not conducting). Q2 presents a
high impedance to the output, keeping the transmitter from transmitting.
When the gate of Q1 is driven low by the input signal, it stops conducting. The gate of
Q2 is then pulled high by R2, turning Q2 on. Q2 presents a low impedance to the output,
keying the transmitter.
Diode D1 attempts to prevent damage to the circuit by blocking the flow of current
should the power input be connected incorrectly.
Warranty
All parts in your kit are guaranteed against defects for one year from date of purchase. This
warranty does not cover damage due to incorrect assembly, improper soldering or wiring,
overvoltage, static damage or other misuse or abuse. If you have problems, please contact me via
email to arrange for an exchange or replacement part. If you accidentally damage a part, don’t
panic – just contact me, replacements are not expensive.
Specifications
Input power:
12V nominal, DC only, 5 – 18 volt range
Input current:
0.2 mA max
Input voltage:
-20 to +20 Volts absolute maximum
Input impedance:
100K Ohms (pull-up to supply voltage)
Output voltage:
30 V max
Output current:
2.5 A DC max continuous (may require additional cooling)
Output ON resistance: Less than 2 Ohms typical
Turn-On time
Less than 1 microsecond
Turn-Off time
Less than 1 microsecond
