11A32

Manuals – Specifications – Links – Pictures

The Tektronix 11A32 is a 400 MHz dual-channel amplifier plug-in for 11000-series scopes.

Key Specifications

Bandwidth	DC to 400 MHz. 100 MHz and 20 MHz four pole BWL (Bandwidth Limit) filters may be selected.
Rise time	875 ps in 1 GHz mainframes such as the 11402, 11402A, 11403, 11403A, DSA601A, or DSA602A
Deflection	1 mV to 10 V per division in 1% calibrated steps
Input impedance	50 Ω or 1 MΩ
Features	High-resolution calibrated DC offset Fast overdrive recovery 5 VRMS overload protection in 50 Ω mode, with manual reset

Internals

Analog

Each input channel has a separate attenuator module containing passive 1 megohm attenuators, a 50 ohm termination resistor, an AC coupling capacitor, a switch selecting the calibrator or signal input, and an M474 buffer amplifier. In normal operation the calibrator signal to the attenuator is instead connected to ground.

The attenuator module output feeds the + input of the M377 amplifier IC through a (blue) 50 ohm transmission line, one per input channel. The cable lengths set a standard delay per plugin.

The M377's − input is connected to the ACVS (Analog Control Voltage System) output.

The (differential) display outputs of the two amplifiers are hard-wired in parallel and drive the mainframe’s 50 Ω per side input impedance. The same is true of the trigger outputs of the two amplifiers.

The version of the M377 used in the 11A32 has a 100 Ω output impedance per side so that two of them in parallel create a source impedance of 50 Ω per side.

Each M377 amplifier's nominal common-mode output voltage is zero whether enabled or not. When not enabled, each M377 differential output is exactly zero by design. This fact is used during calibration by the plugin’s firmware to determine the mainframe’s imbalance and compensate for it during normal operation.

Each of the two channels has its own AUX output on dedicated pins of the plug-in interface connector:

signal name	positive pin number	negative pin number
AUX 1	B38	B37
AUX 2	A36	A35

See also the block diagram below.

Digital

The 11A32 and the 11A34 use exactly the same firmware.

The 11A34 and 11A32 were originally intended to use Intel 8052 microcontrollers. However, during development, the firmware swelled beyond that chip's 8192-byte maximum on-chip ROM size. Doug Haines found an alternate supplier of 8051-compatible chips (OKI Semiconductor) that offered a 16Kbyte on-chip ROM, and that's what the plug-ins wound up with. The finished code size wound up at about 14 KB.

The 11A32 also contains a Dallas Semiconductor DS1220Y NVRAM storing last settings, calibration constants, and instrument serial number. The DS1220Y contains a battery with a typical life time of 20-30 years.

There is also an ACVS (Analog Control Voltage System) sample and hold module on a daughter board that generates the analog voltages needed for gain and offset, including error correction under microcontroller firmware control.

The microcontroller also provides the digital signals sent to the M377 amplifier, setting one of its six fixed gains, one of its three bandwidths, turning on or off its selected output, and each output's normal or invert state.

Digital mainframes do waveform manipulation (addition, subtraction, multiplication, etc.). Consequently only one 11A32 output is on at a time. Analog mainframes however allow more than one channel to be on at a time. This allows the plugin channels to be added or subtracted in the plugin.

Links

• 11A-series plug-in NVRAM replacement
• Tek 11A32 @ barrytech.com

Pictures

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  Block diagram

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  11A32 Main Board Schematic

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  11A32 Main Interface

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  left side internal

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  right side internal

Custom ICs used in the 11A32