The Tektronix M077A  (P/N 155-0059-00) is an HF amplifier monolithic integrated circuit, designed by Thor Hallen. The Tek custom chip catalog calls it a "Gain Trim Amplifier". It comes in a 12 lead TO-8 package and is used in the vertical amplifiers of the 400 MHz and 500 MHz scopes from the 7000 series.

The final vertical gain adjustment is after this amplifier and it typically leads into either a 155-0064-00 or 155-0065-00 output amplifier which drives the vertical deflection plates of the CRT.

Repair issues

Note that this IC can fail by becoming non-linear. It will continue to amplify but will show non-linear gain and clipping when using a step calibrator.

According to Modification 050-0650-00, Vertical HF Amplifier Replacement, the emitter resistors need to be selected according to a code printed on the device.


Used in

Some instruments using part 155-0059-00

Instrument Manufacturer Class Model Description Introduced
7834 Tektronix Oscilloscope 7834 400 MHz storage mainframe 1977
7844 Tektronix Oscilloscope 7844 400 MHz dual-beam non-storage mainframe 1974
7854 Tektronix Oscilloscope 7854 400 MHz waveform-processing scope 1980
7904 Tektronix Oscilloscope 7904 500 MHz non-storage mainframe 1971
7912AD Tektronix Oscilloscope 7912AD 500 MHz digitizer 1978
R7903 Tektronix Oscilloscope R7903 500 MHz non-storage mainframe 1974
R7912 Tektronix Oscilloscope R7912 500 MHz digitizer 1973