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M753 (view source)

Revision as of 03:39, 15 December 2022

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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 used in the [[H2462]] input hybrid which is used several TDS500, TDS600, and TDS700-series scopes.
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 X1, X10, and X100.   
The three attenuators are usually ×1, ×10, and ×100.   
The X1 attenuator is essentially a straight wire or alternatively just a very small attenuation (typically 10%)  
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 X100 attenuator,  
to provide protection to the input JFET.  It is very difficult to make a single ×100 attenuator,  
so the X100 attenuation is usually a second X10 attenuator cascaded with the first as needed.   
so the ×100 attenuation is usually a second ×10 attenuator cascaded with the first as needed.   
The X1 attenuator is often in cascade with the other attenuator(s) and may be located at the amplifier’s input.
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 50 ohm transmission line  
In this configuration, input from the front panel consists of a 50 Ω transmission line  
and three different attenuators (X1, X10, and X100) are attached to this line.   
and three different attenuators (×1, ×10, and ×100) are attached to this line.   
A single 50 ohm resistor serves to terminate the line in the 50 ohm (input impedance) mode.  
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 50 ohm termination is at the BNC and all the other attenuators are disconnected in 50 ohm input impedance mode.
More commonly now, the 50 Ω termination is at the BNC and all the other attenuators are disconnected in 50 Ω input impedance mode.
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