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Browse Prior Art Database

Broadband Tunnel Diode Impedance Converter

IP.com Disclosure Number: IPCOM000091346D
Original Publication Date: 1968-Jan-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 29K

Publishing Venue

IBM

Related People

Bellucci, VJ: AUTHOR

Abstract

The circuit between input terminals 1 and 1' and output terminals 2 and 2' is used to detect voltages in high-speed switching circuits having switching speeds in the range from 0.3 nanoseconds to 2 nanoseconds. The impedance converter is connected to a measuring circuit such as an oscilloscope. The latter is typically represented by a parallel RC circuit as shown.

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Broadband Tunnel Diode Impedance Converter

The circuit between input terminals 1 and 1' and output terminals 2 and 2' is used to detect voltages in high-speed switching circuits having switching speeds in the range from 0.3 nanoseconds to 2 nanoseconds. The impedance converter is connected to a measuring circuit such as an oscilloscope. The latter is typically represented by a parallel RC circuit as shown.

The impedance converter exhibits an input impedance at terminals 1 and 1' which can be made greater than 5,000 ohms. The converter has a voltage gain Vo/Vi approaching values as high as 0.1, a bandwidth from near DC to values approaching 1,000 MHz, and a noise figure less than or equal to 3 db. The converter is capable of handling a dynamic range of approximately +/- 500 millivolts across terminals 1 and 1'.

In order to achieve the desired input impedance Z1 at input terminals 1 and 1' while still maintaining the voltage gain of 0.1, tunnel diode TD is employed as a negative impedance device having a negative impedance Rd. When the converter is used with a measuring system as shown, the input impedance Za across terminals a and a' is given by the equation Za = (Rd)(50)/(Rd + 50). In order to achieve the desired gain, Za must be selected in accordance with the equation Vo/Vi = 1/10 = Za/(4500 + Za).

Using both equations to solve for Rd yields Rd equal to -55.6 ohms. In order to bias TD in its negative resistance region at -55.6 ohms, bias potential E is applied...