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Voltage Scope Probe

IP.com Disclosure Number: IPCOM000073451D
Original Publication Date: 1970-Dec-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

McCabe, JF: AUTHOR

Abstract

The attenuator circuit for use with a scope consists of three stages A, B, and C, all operating in the following configuration. An input signal from a test device is applied between terminals J1 and J2 across a 10 meg: ohm resistor R1. Transistor Q2, wit resistors R2, R3, and R4, capacitors C3, C4, and C5, and zener diode CR2 are connected as a common base current generator at the source of FET transistor Q1. With this arrangement, transistor Q2 provide a high impedance for the source of transistor Q1. Resistor R3 provides a zero DC offset adjustment for the offset operating point of the FET transistor Q1. Stage B comprises transistor Q3, resistor R5 and capacitor C6, C7, C8, and C13 connected as a DC coupled emitter follower which in turn is DC coupled to the base of transistor Q4 of stage C.

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Voltage Scope Probe

The attenuator circuit for use with a scope consists of three stages A, B, and C, all operating in the following configuration. An input signal from a test device is applied between terminals J1 and J2 across a 10 meg: ohm resistor R1. Transistor Q2, wit resistors R2, R3, and R4, capacitors C3, C4, and C5, and zener diode CR2 are connected as a common base current generator at the source of FET transistor Q1. With this arrangement, transistor Q2 provide a high impedance for the source of transistor Q1. Resistor R3 provides a zero DC offset adjustment for the offset operating point of the FET transistor Q1. Stage B comprises transistor Q3, resistor R5 and capacitor C6, C7, C8, and C13 connected as a DC coupled emitter follower which in turn is DC coupled to the base of transistor Q4 of stage C.

Stage C has transistor Q4 connected in an emitter follower configuration with variable resistor R9 connected to the scope input.

Transistor Q5, along with resistors R6 and R7, zener diodes CR3 and CR4, and capacitors C9, C11, and C12 are connected as a current generator in the emitter of the transistor Q4. The use of a current generator in the output stage provides for a wide range of linear operation of the transistor Q3. The attenuator circuit is adjustable by resistor R9 for operation into a 50 ohm load input.

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