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351:= 2 and the amplifier gain is 3. When the circuit is first energized, the lamp is cold and the gain of the circuit is greater than 3 which ensures start up. The dc bias current of vacuum tube V1 also flows through the lamp. This does not change the principles of the circuit's operation, but it does reduce the amplitude of the output at equilibrium because the bias current provides part of the heating of the lamp.
39:
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241:
Simplified schematic of a Wien bridge oscillator from
Hewlett's US patent 2,268,872. Unmarked capacitors have enough capacitance to be considered short circuits at signal frequency. Unmarked resistors are considered to be appropriate values for biasing and loading the vacuum tubes. Node labels and
90:
that not only kept the oscillator output amplitude constant, but it also kept the oscillator's loop gain near unity. The latter is a key technique for achieving a low distortion oscillator. Earlier, Larned
Meacham had used light bulbs in bridge circuits to stabilize and linearize
506:
42:
Insides of the
Hewlett-Packard HP 200A. The light bulb repurposed as a positive temperature coefficient resistor is to the right of the upper section of the variable capacitor, which is the large structure in the
257:, connected in a positive feedback loop between the amplifier output and differential inputs. At the oscillating frequency, the bridge is almost balanced and has very small transfer ratio. The
225:
Through the 1940s and into the 1950s, the subsequent versions of the 200A covered different and wider frequency ranges. The latest version was the 200CD. It covered from the subaudio 5
229:
to the low end (Long Wave) of the AM radio band at 600 kilohertz. The 200CD became a ubiquitous audio generator in engineering laboratories worldwide from the 1950s to the 1990s.
242:
reference designators in this figure are not the same as used in the patent. The vacuum tubes indicated in
Hewlett's patent were pentodes rather than the triodes shown here.
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which reduces the amplifier gain until the point is reached that there is just enough gain to sustain sinusoidal oscillation without over driving the amplifier.
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is a product of the very high amplifier gain and the very low bridge ratio. In
Hewlett's circuit, the amplifier is implemented by two vacuum tubes.
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The product code was chosen to give the impression that HP was an established company. A variation, the HP 200B, was customized for
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440:. Frequency and amplitude stabilization of an oscillator with no tube overloading. Uses tungsten lamp to balance bridge.
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as the temperature-dependent resistor in its feedback network. The light bulb was an inexpensive and effective
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504:, "Variable Frequency Oscillation Generator", published 11 July 1939, issued 6 January 1942
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82:'s masters thesis. It was also the first such commercial oscillator to use a simple
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which is connected to provide positive feedback at the frequency of oscillation. R
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552:"User manual for Model 200A Audio Oscillator, Serial 30223 and Above"
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can be considered as a combination of a differential amplifier and a
226:
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29:
521:"Variable Frequency Oscillation Generator, US patent 2,268,872"
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can be modeled as a non-inverting amplifier with a gain of 1+R
268:
and the non-inverting input is the control grid of tube V
102:, which bought eight units for use in the production of
484:"The 200B Oscillator and Disney Fantasound - HP History"
369:"Hewlett-Packard's First Product: The 200A - HP History"
272:. To simplify analysis, all the components other than R
264:
The amplifier's inverting input is the cathode of tube V
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111:
The circuit diagram is shown in
Hewlett's 1939 patent.
51:, first built in 1938, was the first product made by
569:"The 200AB and 200CD: Always Improving - HP History"
113:
74:used for testing sound equipment. It used the
671:
8:
612:Electronic Circuits: Discrete and Integrated
610:Schilling, Donald; Belove, Charles (1968),
678:
664:
583:"Hewlett-Packard HP-200CD audio generator"
236:
27:Audio oscillator made by Hewlett-Packard
360:
646:This electronics-related article is a
192:less than 1% between 35 Hz and 15 kHz
78:circuit, that had been the subject of
453:Vault guide to the top tech employers
189:less than 1% between 35 Hz and 15 kHz
7:
636:
634:
538:"Model 200A audio oscillator, 1939"
296:and with a high input impedance. R
629:HP200A manual (1951) at HP archive
429:10.1002/j.1538-7305.1938.tb00799.x
410:"The Bridge Stabilized Oscillator"
25:
638:
614:, McGraw-Hill, pp. 612–614
597:"Dating Vintage HP Instruments"
408:Meacham, L. A. (October 1938),
1:
417:Bell System Technical Journal
320:self heats and increases the
650:. You can help Knowledge by
707:Products introduced in 1939
203:less than 75Ω under 15 kHz
148:X100: 2000- 20 000 Hz
728:
633:
456:. Vault Inc. p. 111.
200:less than 75Ω under 15 kHz
142:20 Hz-20 kHz in 3 range
697:Hewlett-Packard products
133:35 Hz-35 kHz in 3 range
70:It was a low-distortion
55:and was manufactured in
450:Pasiuk, Laurie (2006).
702:Electronic oscillators
388:, The Ilex Press Ltd,
251:Wien bridge oscillator
243:
88:automatic gain control
76:Wien bridge oscillator
44:
35:
382:Gordon Laing (2004),
343:then at equilibrium R
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139:X100: 3500- 35 000 Hz
65:Palo Alto, California
41:
33:
214:115 V 50-60 Hz 60 W
164:Calibration accuracy
502:Hewlett, William R.
211:115 V 50-60 Hz 60 W
116:
34:HP 200A front panel
247:William R. Hewlett
244:
114:
45:
36:
712:Electronics stubs
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463:978-1-58131-339-0
322:negative feedback
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16:(Redirected from
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197:Output impedance
146:X10: 200-2000 Hz
137:X10: 350-3500 Hz
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72:audio oscillator
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181:1 W 500 Ω load
153:Scale of dialer
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130:Frequency range
115:Specification:
53:Hewlett-Packard
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623:External links
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652:expanding it
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467:. Retrieved
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175:Output power
167:less than 2%
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80:Bill Hewlett
69:
48:
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255:Wien bridge
221:Development
100:Walt Disney
93:oscillators
691:Categories
498:US 2268872
469:2010-05-10
355:References
186:Distortion
95:in 1938.
84:light bulb
259:loop gain
233:Operation
125:HP 200B
105:Fantasia
312:form a
159:20-200
122:HP 200A
49:HP 200A
43:center.
508:
500:,
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392:
156:35-350
61:garage
18:HP200A
555:(PDF)
524:(PDF)
436:(PDF)
413:(PDF)
335:and C
308:and C
284:and C
648:stub
458:ISBN
390:ISBN
327:If R
47:The
425:doi
339:= C
331:= R
304:, C
300:, R
280:, C
276:, R
249:'s
63:in
59:'s
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421:17
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347:/R
292:/R
227:Hz
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20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
