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M753: Difference between revisions
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The Tektronix M753 is a higher-bandwidth (2 GHz) version of the [[M713]] 1 GHz unity-gain buffer amplifier. | The '''Tektronix M753''' is a higher-bandwidth (2 GHz) version of the [[M713]] 1 GHz unity-gain buffer amplifier. | ||
The M753 is | The M753 is the first amplifier stage in the [[H2462]] input hybrid which is used in several TDS500, TDS600, and TDS700-series scopes. | ||
At the time of the M753's development, [[John Addis]] wrote: | At the time of the M753's development, [[John Addis]] wrote: | ||
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In order to save money, scope input attenuators have been reduced in number over the years to just three | In order to save money, scope input attenuators have been reduced in number over the years to just three | ||
while amplifiers have added either gain switching or internal attenuation to make up for the required missing deflection factors. | while amplifiers have added either gain switching or internal attenuation to make up for the required missing deflection factors. | ||
The three attenuators are usually | The three attenuators are usually ×1, ×10, and ×100. | ||
The | The ×1 attenuator is essentially a straight wire or alternatively just a very small attenuation (typically 10%) | ||
to provide protection to the input JFET. It is very difficult to make a single | to provide protection to the input JFET. It is very difficult to make a single ×100 attenuator, | ||
so the | so the ×100 attenuation is usually a second ×10 attenuator cascaded with the first as needed. | ||
The | The ×1 attenuator is often in cascade with the other attenuator(s) and may be located at the amplifier’s input. | ||
The high frequency response is strictly a function of the path length from the input BNC connector to the JFET input, | The high frequency response is strictly a function of the path length from the input BNC connector to the JFET input, | ||
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There are several advantages inherent in this scheme. | There are several advantages inherent in this scheme. | ||
In this configuration, input from the front panel consists of a | In this configuration, input from the front panel consists of a 50 Ω transmission line | ||
and three different attenuators ( | and three different attenuators (×1, ×10, and ×100) are attached to this line. | ||
A single | A single 50 Ω resistor serves to terminate the line in the 50 Ω (input impedance) mode. | ||
This termination is at the end of the input line instead of at the beginning as with previous attenuators. | This termination is at the end of the input line instead of at the beginning as with previous attenuators. | ||
More commonly now, the | More commonly now, the 50 Ω termination is at the BNC and all the other attenuators are disconnected in 50 Ω input impedance mode. | ||
</blockquote> | </blockquote> | ||