HP (Hewlett-Packard) HP 85660B ユーザーズマニュアル

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 YIG-Tuned Mixer (YTX) Driver, Circuit Description
The YTX Driver receives a voltage proportional to the instrument LO frequency and produces
a signal to control current in the YTX coil.
Input Differential Amplifier 
This input signal to the YTX Driver comes from the A19 DAC and is -3 
 For
example, as the YTO Loop sweeps from 2 to 6 Ghz, this input signal sweeps from -6 to
-18 V. It is buffered by differential amplifier 
 and appears at 
Bandswitch 
The frequency that the YTX is tuned to must be made to follow the first, second, third,
or fourth harmonic of the YTO frequency, depending on the frequency band in which the
instrument is operating. This is done by attenuating the buffered input signal with a voltage
divider as shown in Figure 1.
0
 
0
0
Figure 1. Bandwidth Voltage Divider
The position on the attenuator is determined by the harmonic number in use. The
bandswitching is done with FET 
 Q2, Q3, and 
 The bandswitch information used to
turn on the 
 comes from 
 Slope Generator. R6 and 
 to R14 form a second
voltage divider used as a gate return through R15 to R18. This prevents current through
bandswitch diodes and resistors (for example, 
 and 
 when the associated FET is
switched off from affecting the bandswitch voltage divider R5 and R7 to 
 1