198:, a small input signal gives a larger output signal without any change in shape (low distortion): the input signal causes the output signal to vary up and down about the Q-point in a manner strictly proportional to the input. However, because the relationship between input and output for a transistor is not linear across its full operating range, the transistor amplifier only approximates linear operation. For low
56:
332:: The voltage drop across a portion of a resistance across the plate voltage supply determines the grid bias. The cathode is connected to a tap on the resistance. The grid is connected to an appropriate impedance that provides a DC path either to the negative side of the plate voltage supply or to another tap on the same resistance.
322:: When the grid is driven positive during part of the input frequency cycle, such as in class C operation, rectification in the grid circuit in conjunction with capacitive coupling of the input signal to the grid produces negative DC voltage at the grid. A resistor (the
342:): Initial velocity grid current is passed through a grid-to-cathode resistor, usually in the range of 1 to 10 megohms, making the grid potential around one volt negative relative to the cathode. Initial velocity bias is used only for small input signal voltages.
202:, the transistor must be biased so the output signal swing does not drive the transistor into a region of extremely nonlinear operation. For a bipolar junction transistor amplifier, this requirement means that the transistor must stay in the
142:
such as a diode, transistor or vacuum tube in a circuit in which AC signals are also present, in order to establish proper operating conditions for the component. For example, a bias voltage is applied to a transistor in an
358:
as an impedance converter to drive other electronics within a few meters of the microphone. The operating current of this JFET is typically 0.1 to 0.5 mA and is often referred to as bias, which is different from the
316:) - The voltage drop across a resistor in series with the cathode is utilized. The grid circuit DC return is connected to the other end of the resistor, causing the DC grid voltage to be negative relative to the cathode.
254:
Grid bias is the DC voltage provided at the control grid of a vacuum tube relative to the cathode for the purpose of establishing the zero input signal or steady state operating condition of the tube.
244:
as the transistor reaches saturation or cut-off. The process of obtaining an appropriate DC collector current at a certain DC collector voltage by setting up the operating point is called biasing.
236:
mode, using a variety of circuit techniques, establishing the Q-point DC voltage and current. A small signal is then applied on top of the bias. The Q-point is typically near the middle of the DC
273:, the DC bias voltage is negative relative to the cathode potential. The instantaneous grid voltage (sum of DC bias and AC input signal) does not reach the point where grid current begins.
59:
A graphical representation of the current and voltage properties of a transistor; the bias is selected so that the operating point permits maximum signal amplitude without distortion.
326:) permits discharge of the coupling capacitor and passes the DC grid current. The resultant bias voltage is equal to the product of the DC grid current and the grid leak resistance.
190:
typically require specific DC voltages and currents for correct operation, which can be achieved using a biasing circuit. As an example of the need for careful biasing, consider a
279:
using general-purpose tubes are biased negatively to the projected plate current cutoff point. Class B vacuum tube amplifiers are usually operated with grid current (class B
283:). The bias voltage source must have low resistance and be able to supply the grid current. When tubes designed for class B are employed, the bias can be as little as zero.
363:
interface which supplies 48 volts to operate the backplate of a traditional condenser microphone. Electret microphone bias is sometimes supplied on a separate conductor.
289:
are biased negatively at a point well beyond plate current cutoff. Grid current occurs during significantly less than 180 degrees of the input frequency cycle.
435:
577:
420:
300:: The DC grid potential is determined by connection of the grid to an appropriate impedance that will pass DC from an appropriate voltage source.
126:, is the DC voltage or current at a specified terminal of an active device (a transistor or vacuum tube) with no input signal applied. A
590:
656:
103:) signals, also require a steady (DC) current or voltage at their terminals to operate correctly. This current or voltage is called
355:
675:
241:
229:
203:
223:
35:
237:
159:
293:
There are many methods of achieving grid bias. Combinations of bias methods may be used on the same tube.
680:
270:
108:
138:
In electronics, 'biasing' usually refers to a fixed DC voltage or current applied to a terminal of an
191:
144:
139:
76:
351:
100:
610:
377:
240:, so as to obtain the maximum available peak-to-peak signal amplitude without distortion due to
652:
494:
286:
276:
259:
96:
558:
148:
49:
594:
115:
469:
372:
171:
72:
474:. Washington, D.C.: United States Government Publishing Office. p. 97. TM 11-665.
669:
487:
401:
360:
457:(16th ed.). New Augusta Indiana: Editors and Engineers, LTD. pp. 266–267.
304:
167:
130:
is a portion of the device's circuit that supplies this steady current or voltage.
210:
amplifier, although the terminology differs a little: the MOSFET must stay in the
92:
64:
42:
563:. Indianapolis: Howard W. Sams & Co./The Bobbs-Merrill Company. p. 28.
55:
199:
187:
88:
262:
195:
175:
152:
17:
174:, to improve the quality of the recording on the tape. This is called
48:"Bleeder bias" redirects here. For the safety discharge resistor, see
211:
207:
206:, and avoid cut-off or saturation. The same requirement applies to a
155:
voltage is often applied to the grid electrodes for the same reason.
80:
84:
54:
232:
the bias point is chosen to keep the transistor operating in the
147:
to allow the transistor to operate in a particular region of its
531:(2nd ed.). New York: Rinehart Books. pp. 505, 770–771.
607:
513:
41:"Bias point" redirects here. For the financial term, see
591:"Phantom Power and Bias Voltage: Is There A Difference?"
406:(1st ed.). New York: Tab Books. pp. 450–454.
166:
is also used for a high-frequency signal added to the
75:) operating conditions (current and voltage) of an
486:
493:(2nd ed.). New York: McGraw-Hill. pp.
629:Boylestad, Robert L.; Nashelsky, Louis (2005).
27:Background operating conditions for electronics
468:Headquarters, Department of the Army (1952).
8:
471:C-W and A-M Radio Transmitters and Receivers
640:Basic Electricity and Semiconductor Devices
572:
570:
448:
446:
444:
403:The Benchtop Electronics Reference Manual
395:
393:
633:. Prentice-Hall Career & Technology.
415:
413:
425:, New York: McGraw-Hill, 1957, p. 2-27.
389:
214:, and avoid cutoff or ohmic operation.
118:of a device, also known as bias point,
546:. New York: McGraw-Hill. p. 9-27.
638:Patil, P. K.; Chitnis, M. M. (2005).
631:Electronic Devices and Circuit Theory
111:on this DC bias current or voltage.
7:
647:Sedra, Adel; Smith, Kenneth (2004).
560:Getting the Most Out of Vacuum Tubes
542:Giacoletto, Lawrence Joseph (1977).
107:. The AC signal applied to them is
83:. Many electronic devices, such as
25:
485:Everitt, William Littell (1937).
30:This article is about biasing in
356:junction field-effect transistor
250:Vacuum tubes (thermionic valves)
544:Electronics Designers' Handbook
508:RCA Manufacturing Co. (1940).
422:Electronic Designers' Handbook
1:
453:Orr, William I., ed. (1962).
354:elements typically include a
182:Importance in linear circuits
593:. 2007-02-05. Archived from
527:Ghirardi, Alfred A. (1932).
400:Veley, Victor F. C. (1987).
230:bipolar junction transistors
218:Bipolar junction transistors
79:that processes time-varying
651:. Oxford University Press.
510:Receiving Tube Manual RC-14
151:curve. For vacuum tubes, a
697:
224:Bipolar transistor biasing
221:
186:Linear circuits involving
47:
40:
29:
557:Tomer, Robert B. (1960).
489:Communication Engineering
419:Landee, Davis, Albrecht,
649:Microelectronic Circuits
36:Biasing (disambiguation)
614:(subscription required)
160:magnetic tape recording
676:Electronic engineering
271:audio power amplifiers
71:is the setting of DC (
60:
34:. For other uses, see
576:Landee et al., 1957,
434:Landee et al., 1957,
336:Initial velocity bias
58:
529:Radio Physics Course
265:, and class A and AB
192:transistor amplifier
145:electronic amplifier
140:electronic component
95:, whose function is
77:electronic component
642:. Phadke Prakashan.
352:Electret microphone
170:and applied to the
455:The Radio Handbook
378:Small signal model
287:Class C amplifiers
277:Class B amplifiers
61:
263:voltage amplifier
16:(Redirected from
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269:power stages of
149:transconductance
50:Bleeder resistor
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623:Further reading
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120:quiescent point
116:operating point
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611:Standard 61938
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597:on 2009-09-08.
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373:Idling current
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320:Grid leak bias
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314:automatic bias
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222:Main article:
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172:recording head
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99:time-varying (
73:direct current
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14:
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658:0-19-514251-9
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516:. p. 38.
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361:phantom power
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258:In a typical
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681:Vacuum tubes
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595:the original
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509:
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340:contact bias
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330:Bleeder bias
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319:
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309:
305:Cathode bias
303:
297:
292:
253:
246:
233:
227:
194:. In linear
185:
168:audio signal
163:
157:
137:
128:bias circuit
127:
123:
119:
113:
104:
93:vacuum tubes
68:
62:
31:
18:Bias circuit
347:Microphones
212:active mode
204:active mode
188:transistors
162:, the term
89:transistors
65:electronics
43:Basis point
32:electronics
670:Categories
384:References
298:Fixed bias
200:distortion
196:amplifiers
109:superposed
97:processing
324:grid leak
310:self-bias
238:load line
176:tape bias
153:grid bias
367:See also
242:clipping
134:Overview
578:p. 2-28
495:538-539
436:p. 4-19
260:Class A
124:Q-point
81:signals
69:biasing
655:
234:active
208:MOSFET
85:diodes
122:, or
653:ISBN
228:For
164:bias
114:The
105:bias
91:and
608:IEC
514:RCA
158:In
63:In
672::
569:^
443:^
412:^
392:^
312:,
178:.
101:AC
87:,
67:,
661:.
580:.
497:.
438:.
338:(
308:(
281:2
267:1
52:.
45:.
38:.
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
