7D20

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The Tektronix 7D20 is a two-channel digitizing plug-in for 7000-series scopes. It is a triple-width plug-in and provides both vertical and horizontal signals to the scope.

Key Specifications

Bandwidth 0–70 MHz (DC), 10 Hz–70 MHz (AC)
Rise time < 5 ns
Sampling Rate 40 MSps
Resolution 8 bit
Deflection 5 mV/Div to 5 V/Div (1–2–5)
Input impedance 1 MΩ // 20 pF
Time base
  • 50 ns/Div — 1 μs/Div: Equivalent Time Mode
  • 2 μs/Div — 200 μs/Div: Extended Real Time Mode
  • 500 μs/Div — 50 ms/Div: Real Time Mode
  • 100 ms/Div — 20 s/Div and External: Roll Mode
External clock < 10 kHz
Memory 2 × 455 cells (alternating) analog / 1024 words digital
Features
  • 2 channels
  • 6 memory banks
  • 2 cursors
Weight 3.9 kg (8.5 lb)

Internals

The 7D20 uses an analog shift register (CCD) for high-speed signal acquisition, and then digitizes the stored analog signal at a lower speed (see Patent US 4527117A). This design allowed the 7D20 to capture single-shot events at 40 MSamples/s even though this exceeded the speed of ADCs of the time. The 7D20 can digitally store waveforms and has a GPIB interface. A microprocessor (68B09) in the plug-in controls most of its functions.

The analog waveforms that are sent to the 7000-series mainframe are generated by vertical and horizontal DACs. The DACs outputs can be calibrated for scaling and shift so that signals are accurately displayed on the oscilloscope screen.

The 7D20 has a "roll" mode that emulates a paper roll chart, as if the waveform were being drawn by a pen on the right side of the screen while the paper is being moved to the left at a constant rate. No equivalent to "roll" exists in analog scopes. The Tektronix 2212/2216, 2220/2221/2230 and possibly others also have this feature.

The 7D20 can give NVRAM errors that are often easy to fix.

Links

Pictures

Custom ICs used in the 7D20

Page Class Manufacturer Model Part nos Description Designers Used in
155-0196-00 Monolithic integrated circuit Tektronix 155-0196-00 155-0196-00 trigger 455 7D20
155-0217-00 Monolithic integrated circuit Tektronix M55D 155-0216-00 155-0217-00 variable-gain transconductance amplifier Roy Hayes Einar Traa 335 475 7D20 FG504