THE GENERAL RADIO Exper·menter · Exper·menter Th.is Issue: .All Solici-State,...
Transcript of THE GENERAL RADIO Exper·menter · Exper·menter Th.is Issue: .All Solici-State,...
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
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th [;]Exp rim nt r
fi1guire 1.
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.
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, 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.
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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.
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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.
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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
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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 -
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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
Th
1ne-�quar
due d b t
''e er, i
lo ,l r a
n rat r. B · m a ' trol , h interval b b t at JI 3 1.
or from l milli
lll -
with
r ·-
il · b pr -
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.
, - .
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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
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