M377
The M377 is a Tek-made amplifier integrated circuit designed by John Addis. It is used in the 11A16, 11A32, 11A33, 11A34, and 11A52.
About the M377, John Addis says:
The M377 was a single channel plugin on a chip with 0 V common mode input and output voltages, excellent variable gain control, two four pole bandwidth limits, three outputs which could be separately inverted and turned on or off.
It was the first wideband analog IC with level shift on chip (allowing 0 V common mode input and output and without PNP transistors), first wideband amplifier with any on-chip bandwidth limit selection, first to have more than two fixed gain settings (it has six), and first to require only one transient response adjustment (no thermals), and the first to have a highly linear relationship between a control voltage and gain. It also had excellent overdrive recovery.
The packaged M377 die has the following Tek part numbers:
- 165-2129-03
- 165-2089-06
- 155-2089-05 (11A33)
The M377 has one input (differential) and three differential outputs which are identical circuits. Each output has a its own control pins for:
- Output invert
- Output enable
- High-frequency adjustment. The HF ADJ pins have 2k ohms input resistance to ground. The nominally acceptable inputs are ±1V to ground. Because the input resistance tracks the nichrome standard resistors inside the chip, the input is actually current sensitive, not that it makes much difference. This current affects the standing current in a feedback amplifier and hence its open loop gain. At low frequencies, the gain of the M377 is determined entirely by resistor values. At high frequencies, there is phase shift and changing the open loop gain will also change the closed loop gain, hence the transient response.
This means that the gain of the closed loop and hence the hf gain of the amplifier varies with the current in the HF ADJ input.
| Instrument | Instrument SN range | Part Number | Output R/side | Components on ceramic hybrid |
|---|---|---|---|---|
| 11A32 | B010100 - B031028 | 165-2089-03 | 100 ohms | M377 chip only |
| 11A32 | B031029 - up | 165-2089-05 | 100 ohms | M377 chip only |
| 11A34 | B010100 - B031044 | 165-2089-04 | 200 ohms | M377 chip only |
| 11A34 | B031045 - up | 165-2089-06 | 200 ohms | M377 chip only |
| 11A52 | B010100 - B010179 | 165-2129-02 | 100 ohms | Diode bridge + 50 ohm input R + M377 chip |
| 11A52 | B010180 - up | 165-2129-03 | 100 ohms | Diode bridge + 50 ohm input R + M377 chip |
165-2089-xx Pinout
In the 11A32, DISPLAY output 3, TRIGGER is output 2, and AUX SIG is output 1.
| Pin | Function | Notes |
|---|---|---|
| 1 | GP0 | gain select bit 0 |
| 2 | STB | data strobe for gain and bandwidth limit |
| 3 | +15V | |
| 4 | +Vin | |
| 5 | Analog ground | |
| 6 | -Vin | |
| 7 | Analog ground | |
| 8 | Var Gain | |
| 9 | -5V | |
| 10 | -5V | |
| 11 | Output 1 Invert | |
| 12 | Output 1 Enable | |
| 13 | Analog Ground | |
| 14 | +5V | |
| 15 | Output 2 Invert | |
| 16 | Output 2 Enable | |
| 17 | Output 3 Invert | |
| 18 | Output 3 Enable | |
| 19 | -Output 3 | |
| 20 | +Output 3 | |
| 21 | Output 3 HF Adjust | |
| 22 | -Output 2 | |
| 23 | +Output 2 | |
| 24 | Output 2 HF Adjust | |
| 25 | -Output 1 | |
| 26 | +Output 1 | |
| 27 | Output 1 HF Adjust | |
| 28 | Ground | |
| 29 | Ground | |
| 30 | Ground | |
| 31 | +5V | |
| 32 | -5V | |
| 33 | BP1 | bandpass select bit 1 |
| 34 | BP0 | bandpass select bit 0 |
| 35 | GP2 | gain select bit 2 |
| 36 | GP1 | gain select bit 1 |
Pin function legend
Power pins Ground pins HF signals TTL digital control signals analog control signals
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M377 in an 11A52, as U310 and U410. Each M377 chip has a differential output impedance of 200 Ω. The two chips' outputs are in parallel, driving the output pins of the plug-in with a differential impedance of 100 Ω, or 50 Ω per side.
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Two M377 chips (packaged as part number 165-2129-03) in an 11A52.
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M377 die
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M377 Die pad names and numbers
