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1966 PROCEEDIKGSETTERS 1093

b) nonzero output conductance of the equivalent generator for

th e local oscillator circuit, which occasions small changes in

the effective values of the crysta l mount.

CONCLUSIOK

Our work shows that classical calculations

of a

microwave mixer

diode performances are still valid with an X band intermediate fre-

quency, and that theygive a good value for th e conversion

loss.

Another interest of microwave intermediate requency n re-

ceivers is the drastic decrease of local oscillator noise, and the large

pass band (absolute value) which may be used. This is specially use-

ful in radar systems.3

Smaller conversion loss may be obtainable with junction diodes.4

We think that we can improve these results

by

trying varactors

MME.

LIGEON

E.

PIC

Ecole Nationale Superieure d'Electronique

University of Grenoble

Grenoble, France

and tunnel diodes as microwave mixers.

PhiliDS. vol. 25. no. 8 D D . 209-222. 1963-1964.

8 H. ALlaries. Une installation de radar pour ondes de 4 mm. Rro. Technique

type Ga s Schottky barrier epitaxial diodes with a novel contacting technique,

Proc.

I EEE

Conespondcncc). voL 53, pp. 2130-2131. December 1965

4

D..T. Y ok g and-J. C. I ,' 'Millimeter frequency conversion using Au-8;

Operation of a MOS Transistor

as

a

Variable Resistor

An FET

transistor, operating below saturation, can perform the

function of a variable resistor within a limited voltage range. This

restriction is due to the asymmetry and nonlinearity of its charac-

teristics, especially for reverse drainpolarity. It has been shown

elsewhere tha t

i n

the case of the junction

FET

a perfect symmetry

and

a

remarkable improvement in linear ity is achieved if half of the

drain voltage is fed back to he gate [ l ] , [2]. The following work

shows tha t the same situation holds f o r a

MOS

transistor

if

the sub-

str ate is kept floating.

arrangement where half of the drain-voltage is fed back~to-the -gat;.Foi-G%I

parative purposes, the dc gate-voltage i s

always

adjusted to th e Same value as

Fig.

l a l .

c) Theoretical drain characteristics of an MOS transistor for both

cases

of

Fig. l(a)and (b).

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PROCEEDISGSFHEEEE AUGUST

200

m v l s q u a r e

(a)Drain-current vs. drain-voltagecharact eristic s of

a

p-channelenhancement

MOS transistor (Vr= -3 V) for VG

=

-3.1 V.. -3.5 V, and

5 V.

2 V l s q u a r e

(c) Drain characteristics of the sam e tran sistor as n Fig. 2(a).

Fig. 2.

200 m v l s q u a r e

(b) The Same as Fig. 2(a) but with

50

percent feedback from drain to gate

as shown in Fig.1 b)

2

V s q u a r e

(d) The Same as Fig. P(c) with the feedback arrangement

of Fig.

1

b).

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