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

The YTX Driver receives a voltage proportional to the instrument LO frequency and produces
a signal to control current in the YTX coil.

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 

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.

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