the general radio exper·menter exp 1966_0… · note that the shape of the dis ... siderable...

THE GENERAL RADIO

Exper·menter

Th.is Issue:

.All Solici-State, :I,.,ovv-Distortion. Oacilla.tor

Sine Sq us.red. Pu.lsea

VOLUME 401 • NUMIBER 3 / MARCIH 19661

www.americanradiohistory.com


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10 Hz TO 100 kHz

ALL-SOLID-ST ATE, LOW-D�STORTION OSCILLAT,OR

SINE- OR SQUARE-WA VE

The Type 1309-A is the second in our new line of general-purpose varioble-copocitanc.e-tuned RC oscilla�ors, recently introduced with the Type 1 31 0-A Oscillator.1 It continues the modern, all-solid-state design used in the Type 1308-A and Type 131 1 -A Audio Oscillators.

Th r r a.· 'Ura •y th

re

inn we tuipm

hi 1uipm

mea ·ur m nt._, in und-r cording quipm nt · nd h u r quir m nt. on

mu ·t

m, h· \T all 1

t rti n

, and an 1 Rob rt E. wen. '' :\Io ern, \'id -Rn.no:e RC O_cillntor," G neral Ro.dio E.rperimn1ter,. ug 1 HI,·.

C'::> • n ial par f any harm 111 · mea ur ment i a l w- Ii

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@ 1966- GENER.A.L 1RADIO COMPANY, WEST CONCORD, MAS·s., U.S.A.



DIFFERENTIAL WIEN BRIDGE AMPLIFIER

��

March 1966

Figure 2. Block diagram of Type 1309-A Oscillator.

SCHMITT � CIRCUIT

�------,-.---- ----., I I

20-dB VARIABLE

ATTENUATOR 0 v

SYNCHRONIZATION

general laboratory use. Output is quite constant over the entire frequency range of 10 Hz to 100 kHz, and an output attenuator provides the low signal levels necessary for testing active devices. As with other General Radio RC Oscillators, ther is an input-output synchronization jack. An added feature IS a quare-wave output for transientrespon e measurements. This output has a ·symmetrical waveform and an unusually short rise time.

Figure I is a panel view of the o cillator, and Figure 2 shows the three major element : a low-distortion Wien bridge oscillator, a Schmitt squaring circuit, and an output attenuator.

DISTORTION

The low distortion IS achieved through the use of a high degree of negative feedback and a thermistor of 2 Robert E. Owen, "Solid-St9.te RC Oscillator Design for Audio Use", Journal of the Audio Engineering Society, Vol 14, January, 1966.

0.3

� "'

0.2

� ""�

�0.1

0 IOHz 20

� � -r---_

50 100 200

SPECIFICATION

\YPICAL

500 I kHz 2 FREQUENCY

60-dB

STEP ATTENUATOR

Goon OUTPUT soon

p cial de ign for amplitude control.2 The distortion at full output is approximately constant with load imp danc for any linear load of 600 ohm or greater. When the open-circuit output i one volt or le , the distortion i ind pendent of the size of the load. The distortion is typically le s than 0.01 % for frequencies near 1 kHz, often b low what can be conveniently measured. Note that the shape of the distortion curve ( . igure 3) i typical of most audio-frequency devices, so that the margin betw n the source di tortion and a device under test remain approximately onstant with .frequ ncy.

Low level of hum and nois are always de irable, but to be useful for broadband distortion measurem nts an oscillator mu t have noise and hum that are at lea t a low as the distortion. The 1-kHz output of the TYPE 1309-A ha noi e typically le s than 0.005o/0 in a bandwidth of 5 Hz to 500 kHz, and

5

/ /

v /

l� 10 20

.I v

50 100 lr.Jo•-si

Figure 3. Oscillator distortion for 600-ohm load or open circuit.

3



4

the l�IExperimenter

� +2.0..-----.--------.---r----r-----r----r-----,-----..----r----r------.-------. :::J Q.._ � +1.0 t----+-----+--+----+----+---+----+----+---+----+-----+-� of!. �z o l::::=:::f----+--f=�=t---�-+��t-�-f-"""""'-===='==---i----==f======t=-� j:::-:5 -1.0 1-----+----+---t-----t-----+--t-----t-----+--t-----t----t-----l ILi a: -2.0 ,___ _ _.__ __ ___.._ __ ..__ _ _._ __ __._ __ ..__ _ _._ __ ___.._ __ ...__ _ _._ __ ___..__-----J

10 Hz 20 50 100 2.00 500 lkHz 2 5 10 20 50 100 FREQUENCY lt.Jo9-tKI

Figure 4. Typical oscillator output voltage versus frequency,

hum is less than 0.001 % ( -100 dB)

of the full output.

ATIENUATOR

The sinusoidal open-circuit output voltage can be varied continuously between 5 volts and less than 0.5 millivolt by means of the output attenuator. An additional position, labeled zero volts, disconnects the oscillator output from the terminals yet maintains the 600-ohm output impedance. This pro

vides a convenient transient-free means

of reducing the output to zero without disturbing the continuous attenuator setting or shorting or disconnecting a carefully shielded system. Further, it

aids in locating ground loops and other sources of extraneous signals when one is working with small signal levels. With the oscillator output removed, the extraneous signals are not masked, so that they are easier to measure and to eliminate. This technique offers con

siderable advantage over the oftenused one of short-circuiting the output. Shorting drastically changes the im-

pedance levels and can, in effect, change

the whole circuit, possibly eliminating the very source that one is trying to isolate.

The variation of the output of any oscillator at different frequencies is perhaps its most noticeable departure

from ideal. Because of this, and because a constant output is convenient for response measurements, most modern transistor oscillators have relatively flat output-frequency characteristics, although this property may be accompanied by moderately high distortion, which is uniform across the frequency range. The output of the TYPE 1309-A is constant within ±2% over its whole frequency range and is typically within ±0.5% (see Figure 4). It is stable

within ±0.2% for one hour, typically, under normal laboratory conditions and after warm-up.

One position on the step attenuator connects the high-speed Schmitt circuit

to the sinusoidal oscillator. Symmetrical, positive-going square waves with a

rise time of less than 100 nanoseconds

Figure 5. (Left) Leading edge of 10-kHz square wave into 50-ohm load. Horizontal scale: 50 ns/div. (Right) Direct-coupled 10-Hz square wave has flat top. Horizontal scale: 10 ms/div.



into 50 ohms are then available at the

output terminals. This rise time is

typically 40 nano econds into 50 ohms

at full output, which corresponds to the

response time of an amplifier with

greater than 10-MHz bandwidth. (See

Figure 5.) This output is greater than 5 volts, peak-to-peak, open-circuit, and

is de-coupled through the 20-dB attenuator, so that the waveform is flat

topped even at the lower frequency limit of 10 Hz.

SYNCHRONIZATION

This oscillator has a combination input/output synchronization capabil

ity similar to that described for the TYPE 1310-A 2-c to 2-Mc Oscillator1 and its usefulness is enhanced by th� high purity of the oscillator output. The

sync output is greater than 1.5 volts . . '

open-c1rcu1t, behind 12 kilohms and is in phase with the normal front-panel

output..

This output is particularly

convenient for triggering counters and

tone-burst generators, etc, when the

attenuator output is set at a very low

level. Because this output is always

connected to the sinusoidal oscillator '

both square-wave and sinusoidal out-

puts are available simultaneously. The

square waves expand the uses of the

synchronizing capability by providing an output waveform and amplitude

that are independent of the input

waveform. Figure 6 shows a further use

of the combined synchronization and

square-wave functions.

1Ibid.

Figure 6. Using phase-shift capability of synchronized oscillator lo gel variable time dehiy pulses. (Top) sinusoidal input to oscillator synchronization jack. (Middle) Square-wove output with adjustable phase. (Bottom) Differentiated square wave (pulse) that has been adjusted to follo w zero crossing of input sine wave by ap-

proximately 20°.

March 1966

Robert E. Owen received his B.E.E. from Ren -selaer Polytechnic Institute in 1961 and his M. .E.E. from Case Institute of Technology in 1963. During his student career, he was employ d summers by Dresser Electronic and Boonton Radio Corporation. He came to General Radio as a . developm�nt ngineer m 1963. His field is elec:tri al networks, both active and passive.

APPLICATIONS

The variety of uses for an oscillator

with this frequency range and types of

waveforms is almost unlimited. Its

purity of waveform and range of avail

able output level, however, make it

particularly valuable for laboratory design and measurement use. As an

example of its versatility, it can be used

in audio amplifier measurements as a

source: with a wave analyzer to measure hum

noise, and harmonic distortion· '

. '

with another oscillator and a wave

analyzer to measure intermodulation distortion;

with a tone-burst generator and

oscilloscope to measure overload recov

ery and peak power output;

with an oscilloscope to measure

transient response ;

with a wattmeter to measure power output; and

with a voltmeter to measure fre-

quency response. -R. E. OWEN

5



6

t rim nt r

•

SPEC FICATIO s

Figure 7. The Type 1309-A Oscillator and associated eq1u1ipment used for testing of an ·audio amplifier •

FREQUENCY Tli�h-im Rang : JO Hz to 1 kHz in four decad rnn11: . Control: ontinuc usly ndju bl• nl' in dial

ov r r n in 1 ur l, ' rni r in �..1' urn,.

A ccuracy: ±2 <

OUTPUT

Sine Wave

Square Wave

Voltage: ir " p n- ircuit. r

Control: ad ju r

p · k-t - ak,

l. T. •piculJy

on inuou ly

Power: l m\' int 60 - U lo d. over ' h l fr qu ncy rt'mg

Voltage: 5.0 V ±5%

Impedance: •

:\finimum

Frequency Cttarac:leristlc: ±2% fr qu ncy rung for l ad of · 0

c typfral ·ur in l· igur ·I.

un<l

Hum: L than .5 f ting. (0.001 °7a

Catalog • ·umbt·r

nuator

GENERAL

T rminals: Two . p r un d.

Accessories ord, p

Dimensions: inche (210

Nel Weight:

Supp led: fuse .

D . criplion 1309-9701 l 560-9695 0480-9638

Type 1309-A Oscillator, 10 H:z:-100 kH:z: Type 1560-P95 A daptor Cable Type 480-P308 Rack-A daptor Set

� : Binding Post , one

T ·p P-22 P wer

125 , 200

Price in C A $325.00

3.00 7.00

250 V,

1 -



March 1966,

GENE:RA TION OF SINE-SQUARE!D PULSES WITH THE TONE B,LJRST GENERAT01R

'ine- quar d ar u flint

or rais d-c in , pul... "

tincr broad 1 and tr n -t nd in

tri orr

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or from l milli

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with

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Ton -Burt

\Vi th a tim d · ,n trol. - l 1ar ul rith

rator pr c ed a ·

w. :

1.

wee1

1 onn a -- -µF ·ap cit r bc-

fnz upper t rminal of h AL

(left) Figu.re 2. Q,necyc:le s1i1ne-wave burst. (Center) Figu,re 3. One.cycle burst ,gated Qf peak. (Right) Fig ure 4.

Sine-squared pulu!.

� Q ;! � Ef>--��---c->r��-+--��--1 ::r c

ZI �f '"AE0U£HC.Y

41 51

Figure 1. Spectrum envelop,es ,of a rect,ang,ular pulse and a sine·-sq1uared pulse.

TI nN L P TT ::ur I -p ·T and �. App] a ign al of th d ir �cl , r -

l n ·y, mjnaL.

:3,

.r 0 h LP T l r-

l 0 h .ATE D RA'Il ?-.T witche. 0 :....

4. •' 'Y ' E

Nr.· ·E. Thi pr

·imiJar th no ill cop .

'. Byman 'l'RI T f R LEYEL ntr l, hanO'

t �fl

bur t ·

n on

h and h

ph , c of the put e o tha ga ing o a p ak p int , a in Figur :3.

ur

1 Nehon, .Jo3eph i:.;, "Televi ion and ine- <1110.red T ting."' Tektronix rvire rop , April J9<i-L 2 Col.in Cherry, Pulses and Tra11sie11tir in tnnmuniration CircuitR, Ch pman and Hall, L .. Lond n, 19-1 , pp 175-1 l.

, - .

7



the

th �E perim nt r

G. Add a de oltage ource m r1 s

with the inpu ig al n adj u t thi volt g t r move the st ep part of

h 'vav form und to produ e h 1n -quared pu e of Figur

7. e GATE DURATlOA -CLO 'ED wit h to d sired ·ycl in .rvul bet \ n pul e . Alternatively, if a co tinuousl

a ju'tabl int rv l is wanted, t to Xlor XIO andadju t'l'IM ncontrol to d ·ired inter ral.

value of the c pa itor betw n he ign l and timing input is no

-ri ical. It purpo i · o hif the pha of th iming ignal r l ti e to th m-

p u t o hat '"h witching c ur · a th p ak point th input •ir ·ui are

Figure 5. Typic<1I sine-squ<1red pulse train prod,uced with the Tone-Burst Generator.

E P r· e te

COM ANY WEST CONCORO, MASSACHUSETTS 01781

,Jam � K . . -.killing i� a 1953 graduate· r1f tht• l -niiv rl'i \ of 11 I if rniu. at Berk ;le:-i , \\ ith n B.' in El cfri('al Enj.i;illf'eri ng. fk r c iv<'d hi.· l\1 � from JohnA Hopkinl4 11ivc1« itv in 1. 63. He haH I> 'en a j mior ·ngin •er at. l )ougl s Aircraft ·tnd i n

in�trudor in rlec- ronic·� ilt thr l . �- :::-.;: va.1

caclemY. Si11 ·� 1! -9 h ·

ha.· bC'ei1 a de\·elopmC?nt ngin er a.1 enen I TI a

dio, 'P eializing in pull" t ehniqu f: and (•irc·uit�.

\\'orkin t l v 1 ome' hat elow p ak. This ensures more r liable op ra ion.

Th outpu ampli ud mu b lim

it d to 7 vol , p ak- o-peak. becau h input is d - oupled. Th output

ha a de component, whi h can blo k d by a co piing ·apa it r.

,< igure .5 i n o cillogram of typi al

ine- qu r d pul e g n rated in h

manner d crib d abov . Th funda

m n al inpu freq u ncy 1 approx1-mat ly 2.5 kHz and he int rval between puls i 7 p riod .

.T. IC



the general radio exper·menter exp 1966_0… · note that the shape of the dis ... siderable...

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