ACVS

Tektronix 11000-series plug-ins contain a subsystem called the Analog Control Voltage System (ACVS). The ACVS produces several independently controllable DC voltages. The voltages are fed to the analog signal path circuitry (e.g., the OFFSET input of the M377, or the OFFSET pin on the TekProbe input connector. The number of voltages produced by the ACVS depends on how many channels the plug-in has. The 11A34, which has four channels, has an ACVS that produces sixteen control voltages.

The ACVS comprises three parts:

• AD667 12-bit DAC (single output)
• CD4051 analog switches and holding capacitors, implementing a set of sample and hold circuits
• TL074 JFET-input opamps, providing a set of unity-gain output buffers

The output from the DAC is sampled and held, and the buffered voltages are fed to the rest of the plug-in. The voltages in the sample and hold are periodically refreshed. The sample and hold and output buffers are on a daughterboard. (See photo below)

The ACVS is controlled by the M382 chip, which also implements SDI and sequences the amplifier output enable signals.

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  ACVS sample-and-hold circuits on daughterboard on 11A32