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M474: Difference between revisions
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{{Monolithic IC | |||
|Manufacturer=Tektronix | |||
|Model=M474 | |||
|Part_nos= | |||
|Description=amplifier | |||
|an=an | |||
|Used_in=11A32;11A34; | |||
|Designers=John Addis;Ivan J. Cousins; | |||
}} designed by [[John Addis]]. | |||
The M474 is the front-end buffer amplifier used in the attenuator modules of the [[11A32]] and [[11A34]]. | The M474 is the front-end buffer amplifier used in the attenuator modules of the [[11A32]] and [[11A34]]. | ||
Regarding the M474, John Addis recalls | Regarding the M474, John Addis recalls | ||
<blockquote> | <blockquote> | ||
I started the design and Ivan “John” Cousins made a very important contribution to it, | I started the design and [[Ivan J. Cousins|Ivan “John” Cousins]] made a very important contribution to it, | ||
namely the addition of Q47 and Q48 and carried it into production. | namely the addition of Q47 and Q48 and carried it into production. | ||
The IC is within the dashed lines. | |||
Outside the dashed lines are two JFETs (probably a matched pair of chips) and a (Tek-made?) fast PNP chip. | The IC is within the dashed lines. Outside the dashed lines are two JFETs (probably a matched pair of chips) and a (Tek-made?) fast PNP chip. | ||
This schematic is of a hybrid, showing the stray inductances. | This schematic is of a hybrid, showing the stray inductances. | ||
If I remember correctly, the M474 hybrid is separate from but next to the attenuator hybrid inside the attenuator assembly. | If I remember correctly, the M474 hybrid is separate from but next to the attenuator hybrid inside the attenuator assembly. | ||
The M474 likely tested and trimmed (resistors not shown here) for dc balance before being mounted next to the attenuator hybrid. | The M474 likely tested and trimmed (resistors not shown here) for dc balance before being mounted next to the attenuator hybrid. | ||
R15 is likely trimmed when the M474 is in wafer form. | R15 is likely trimmed when the M474 is in wafer form. R15, R1, R2, and circuitry create the 50 Ω output impedance to match the | ||
R15, R1, R2, and circuitry create the | 11-inch 50 Ω [[Peltola connector|Peltola cable]] from the attenuator to the [[M377]] input. | ||
to match the 11 inch | |||
The attenuator would have been trimmed for input C, attenuation, | The attenuator would have been trimmed for input C, attenuation, | ||
| Line 21: | Line 30: | ||
This reduces the JFET capacitive loading on the attenuator, makes compensation independent of input signal and, | This reduces the JFET capacitive loading on the attenuator, makes compensation independent of input signal and, | ||
more importantly keeps the dc linearity of the whole buffer amplifier good for | more importantly keeps the dc linearity of the whole buffer amplifier good for | ||
the | the ±2 V of possible input signal given the ±1 V of DV offset applied to the M377 (11A32/11A34 input amplifier). | ||
At the time I did not know how to make a Zener diode-like voltage source (that came in the [[M377]]), | At the time I did not know how to make a Zener diode-like voltage source (that came in the [[M377]]), | ||
| Line 30: | Line 39: | ||
<gallery> | <gallery> | ||
11A32,34 attenuator hybrid and M474.jpg|Schematic of M474 and surrounding components | 11A32,34 attenuator hybrid and M474.jpg|Schematic of M474 and surrounding components | ||
Tek 11a32 attenuators.png|M474 and surrounding components designated by " | Tek 11a32 attenuators.png|M474 and surrounding components designated by "×0.95" and highlighted in red. The 50 Ω resistor to the right of the amplifier symbol is actually inside the M474. | ||
</gallery> | </gallery> | ||
[[Category:Tektronix-made monolithic integrated circuits]] | [[Category:Tektronix-made monolithic integrated circuits]] | ||