6.2.2 Bridge-Mono Operation; 6.2.3 Parallel-Mono Operation; 6 Principles of Operation- Page 17

Micro-Tech Series

 Power Amplifiers

page 17

Operation Manual

To further protect the output stages, the pat-
ented ODEP circuitry is used. It produces an 
analog output proportional to the always 
changing die temperature of the output transis-
tor. This output controls the translator stage 
previously mentioned, removing any further 
drive that may exceed the safe operating area of 
the output stage.

Thermal sensors S100 and S200 give the 
ODEP circuits vital information on the operat-
ing temperature of the heat sink on which the 
output devices are mounted.

Should the amplifier fail in a way that would 
cause DC across the output lead, the DC pro-
tection circuit senses this on the negative feed-
back loop and shuts down the output stage 
drive until the DC is removed.

6.2.2 Bridge-Mono Operation

By setting the back panel stereo/mono switch 
to Bridge-Mono, you can convert a Micro-Tech 
amplifier for bridged-mono operation. With a 
signal applied to the channel 1 input and the 
load connected between the positive (+) output 
terminals, twice the voltage can be delivered to 
the load.

The channel 1 output feeds the channel 2 error 
amp U204-A. The signal feeding channel 2 is 
inverted so the channel 2 output will have the 

opposite polarity of channel 1. This makes it 
possible to deliver twice as much voltage to the 
load while the protection mechanisms for each 
channel continue to work independently.

6.2.3 Parallel-Mono Operation

With the stereo/mono switch set to Parallel-
Mono, the output of channel 2 is paralleled with 
that of channel 1. A suitable jumper capable of 
handling high current must be connected 
across the positive (+) output terminals to gain 
the benefits of this operating mode.

The signal path for channel 1 is the same as 
previously discussed, except that channel 1 
also drives the output stage of channel 2. The 
balanced input, error amp, translators, and 
LVAs of channel 2 are disconnected and no 
longer control the channel 2 output stage. The 
channel 2 output stage and protection mecha-
nisms are also coupled through S1 and func-
tion as one.

In Parallel-Mono mode, the amplifier can 
deliver twice the current of a single channel. 
Because the channel 2 ODEP circuit is coupled 
through S1, the amplifier gains additional pro-
tection if a fault occurs in the channel 2 output 
stage. The channel 2 ODEP circuit will limit the 
output of both output stages by removing the 
drive from the channel 1 voltage translator.

6 Principles of Operation