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Tektronix 11A34
Quad channel 300 MHz amplifier
Tek 11A34

Compatible with 11000-series scopes

Produced from 1987 to (?)

Manuals – Specifications – Links – Pictures

The Tektronix 11A34 is a four-channel vertical amplifier plug-in for 11000-series and DSA600-series scopes.

Option 23 added four P6134 probes.

There is also a version for video applications, the 11A34V, that was introduced in 1991 (see also 11T5H). It differs from the 11A34 only in its input impedance (75 ohms). Development of the 11A34V was managed by Murlan Kaufman.

more information about 11A34V needed

Key Specifications

Bandwidth DC to 300 MHz. 100 MHz and 20 MHz four pole BWL (Bandwidth Limit) filters may be selected.
Rise time 1.2 ns in 1 GHz mainframe such as the 11402, 11402A, 11403, 11403A, DSA601A, or DSA602A
Deflection 1 mV to 10 V/div in 1% calibrated steps
Input impedance 50 Ω or 1 MΩ
  • High-resolution calibrated DC offset
  • Fast overdrive recovery
  • 5 VRMS input overload protection in 50 Ω mode, with manual reset



Each input channel has a separate attenuator module containing passive 1 megohm attenuators, an AC coupling capacitor, a switch selecting the calibrator or signal input and an M474 buffer amplifier. The calibrator signal turned off inside the plugin when not in use.

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 four 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 four amplifiers.

The version of the M377 used in the 11A34 has a 200 Ω output impedance per side so that four of them in parallel create a source impedance of 50 Ω.

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 four 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
AUX 3 B32 B33
AUX 4 A32 A31

The AUX signals emerge from each M377 amplifier as differential signal with a 200 Ω source impedance per side. External (on the circuit board) 66.5 Ω shunt resistors on each AUX output bring this down to the 50 Ω source impedance specified by the 11k plug-in interface.

See also the block diagram below.


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

The 11A32 and 11A34 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 11A34 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 are also two ACVS (Analog Control Voltage System) sample and hold modules on two daughter boards that generate 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 + up or invert state.

Digital mainframes do waveform manipulation (addition, subtraction, multiplication, etc.). Consequently only one 11A34 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.



Custom ICs used in the 11A34

Page Class Manufacturer Model Part nos Description Designers Used in
M377 Monolithic integrated circuit Tektronix M377 165-2129-03 165-2089-06 155-2089-05 amplifier John Addis 11A16 11A32 11A33 11A34 11A52 2245 2245A 2247 2247A 2252 TDS410 TDS420 TDS460 TDS520D TDS540D TDS580D TDS680C TDS684C TDS714L TDS724D TDS754D TDS784D
M474 Monolithic integrated circuit Tektronix M474 amplifier John Addis Ivan John Cousins 11A32 11A34