60_Hz_ADJUSTABLE_Q_NOTCH

Published:2009/7/2 7:37:00 Author:May

Connection shown for two SN72310 voltage-follower opamps provides attenuation of 60-Hz power-line frequency. Setting of R4 determines a of filter.- The Linear and Intelface Circuits Data Book for Design Engineers, Texas Instruments, Dallas, TX, 1973, p 4-39.   (View)

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NARROW_BANDPASS_FOR_SPEECH

Published:2009/7/2 7:36:00 Author:May

Simple audio filter provides about 20-dB gain at bandwidth of 80 Hz Bandwidth can be narrowed tolimits of unintelligibility by adjusting 10K pot.Input is plugged into phone jack of receiver, and headphones are connected to output. Transistors are SK3004 or equivalent.-Circuits, 73 Magazine, Jan.1974 p 125.   (View)

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VARIABLE_Q_FOR_CW

Published:2009/7/2 7:35:00 Author:May

Fixed-frequency active filter gives slowly rising and falling keyed waveform with good slope considering narrowness of bandwidth, which is 75 Hz at 3 dB down. Adjusting Q with 1K pot changes bandwidth.-A.F. Stahler, An Experimental Comparison of CW Audio Filters, 73 Magazine, July 1973, p 65-70.   (View)

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TWO_STAGE_CW

Published:2009/7/2 7:33:00 Author:May

Uses diode threshold detector between stages to prevent weak undesired signals from passing through until CW signal of desired frequency is present, so as to provide quiet tuning between signals. Bandwidth of filter is sharp (16 Hz), and keyed waveform is good. Gain is near unity, and frequency and Q are both fixed.-A. F. Stahler, An Experimental Comparison of CW Audio Filters, 73 Magazine, JuIy 1973, p 65-70.   (View)

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42667_MHz_MOSFET

Published:2009/7/2 7:26:00 Author:May

Unusual crystal-controlled oscillator, similar to modified Pierce oscillator that uses crystal between grids 1 and 2 of tetrode tube, can be used as local oscillator in VHF and UHF converters. No trimming ortuning is required to get overtone frequency. If fundamental of crystal is desired, increase RFC1 to 100 μH or replace it with 1K resistor. Stability is excellent. Circuit works well with supply as low as 4 V.-G. Tomassetti, Dual-Gate MOSFET Offers an Unusual Crystal-Controlled Oscillator Concept, QST, June 1976, p 39.   (View)

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UP_TO_30MHz

Published:2009/7/2 7:10:00 Author:May

Simple single-transistor PF oscillator is easily assembled from noncritical parts, Tuning capacitor and coil determine frequency.-Circuits, 73 Magazine, July 1977, p 35.   (View)

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GENERAL_PURPOSE_UP_TO_10_MHz

Published:2009/7/2 7:09:00 Author:May

Variation of Colpitts oscillator uses negative feedback at all frequencies at which LC network does not provide phase inversion and voltage step-up.Choose values for coil and capacitors to give frequency desired. R3 serves as regeneration control and for changing waveform of output.-G. W. Short, Good-Tempered LC Oscillator, Wire-less World, Feb. 1973, p 84.   (View)

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GATED_5_MHz_RELAXATION

Published:2009/7/2 7:03:00 Author:May

Output always startsVin same phase with respect to gating signal. Frequency-selective network R1-R2-C provides positive feedback around MC15456 gatecontrolled wideband amplifier.-F.Macli, IC Op Amp Makes Gated Oscillator, EDN Magazine，Sept. 1, 1972, p 52.   (View)

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SPIKE_REJECTlON

Published:2009/7/2 5:33:00 Author:May

Used to eliminate noise that may be present on signal Iine. Based on sampling input Iine at fixed time after each detected transition. If transition was due to noise spike, spike will no longer be present and true signal level will be sampled. lf transition was caused by desired legitimate signal, sampled waveform represents true signal delayed by pulse width of mono MVBR. Mono pulse width is about 12μs. Article gives circuit waveforms and describes operation in detail.-A. S. Bozorth, Pulse Verification Yields Good Noise Immunity. EDN Magazine. Nov. 5. 1973. p 75 and 77.   (View)

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TTL_INrERFACE

Published:2009/7/2 5:31:00 Author:May

MotoroIa MPQ 6001 quad complementary-pair transistor IC serves as interface between TTL gateand diodebrldge used as signal gate. Propagation delay from leadingedge of gate drive pulse until bridge gate opens is 30 ns, with negligible delay between complementary outputs. Used in providing low-level burst of input signal when making response ime measurement.-R. W. Hilsher, Universal Interface: TTL to Diode Array, EDN Magazine, March 5, 1975, p 74 and 76,   (View)

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SCHMITT_USING_7400_GATES

Published:2009/7/2 5:20:00 Author:May

Uses two sections of 7400 quad NAND gate. Will accept input voltages of 10-50 V P-P with values shown, but can use line voltage directly if input resistor is 22K and feedback resistor is 220K. Diode in DC supply limits positive-going input to 5.7 V forprotection of input circuit. Used as interface between 60-Hz line and frequency divider having TTL logic, when 1-s time base is required for timing applications.-W. A. Palm, Connect a 7400 Gate as a Schmitt Trigger, EDN Magazine, Aug. 20, 1976, p 84.   (View)

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OR_LOGIC_FOR_MUTlNG

Published:2009/7/2 5:17:00 Author:May

Connection shown for National LM389 combination of three transistots with opamp gives standard OR circuitfor controlling muting transistor in audio system.Shorting pin 12 of opamp to ground gives NOR logic.- Audio Handbook, National Semiconductor, Santa Clara, CA, 1977, p 4-33-4-37.   (View)

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ACTIVE_CW_FILTER

Published:2009/7/2 5:17:00 Author:May

Modifications made on MFJ Enterprises OWE-2 active audio filter per mit maximum flexibility. Circuit provides fixed bandwidth of 180 or 110 Hz centered on 750 Hz, or optional variable bandwidth for which center frequency can be adiusted in range of 280 to 1590 Hz.-H. M. Berlin, Increased Flexibility for the MFJ Enterprises CW Filters, Ham Radio, Dec. 1976, p 58-60.   (View)

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MOS_TO_TTL_DRIVER

Published:2009/7/2 5:14:00 Author:May

National DS75450 dual peripheral driver serves as interface between different logic types while providing highspeed switching and 300-mA output current per section Requires only single 5-V supply- Interface Databook, National Semiconductor、Santa Clara,CA,1978,p3-20-3-30   (View)

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10_kHz_VOLTAGE_TUNED_

Published:2009/7/2 5:14:00 Author:May

High-Q circuit using Optical Electronies 9831 opamp has sharp resonance, as required for analysis of spectrum of incoming signal. Reverse-biased silicon junctions senre as voltage variable capacitors for sweeping center frequency over 3: 1 range. Values shown for three resistors in twin-T network give cenW frequency of 10 kHz.- Voltage Tuned High-Q Filter, Optical Electronics, Tucson, AZ, Application Tip 10207.   (View)

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10_Hz_HIGH_PASS

Published:2009/7/2 5:13:00 Author:May

Equiterminated Butter-worth high-pass ladder filter has corner frequency of 10 Hz and output impedance level of 16K. Opamps are matched pair in single ML747 package. Article covers design procedure based on use of generalized impedance converters and gives frequency response curve.-L. T. Burton and D. Treleaven, Active Filter Design Using Generalized Impedance Converters, EDN Magazine,Feb. 5,1973,p 68-75.   (View)

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THREE_LOUDSPEAKER_CROSSOVERS

Published:2009/7/2 5:12:00 Author:May

Active filter network splits AF input into three frequency bands each feeding separate 30-W power amplifier. Design allows adjustment of any part of frequency characteristic to any desired level and gives choice of slopes in any part of frequency band. Article gives design equa-tions and construction details. PNP transistors can be BCY70, BCY71, BCY72, or 2N3906. Article also gives circuit of suitable 30-W amplifier.-D. C.Read, Active Filter Crossover Networks, Wireless World, Dec.1973, p 574-576.   (View)

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60_Hz_NOTCH_FILTER

Published:2009/7/2 5:10:00 Author:May

Design is based on passband gain of 3 and O of 6. Resistors can be 5%.Opamps can be 741. Notch response is obtained by subtracting output signal of bandpass filter from its input signal whh R6.-H, M. Berlin, Design of Active Filters, with Experiments, Howard W. Sams, Indianapolis, IN, 1977, p 155.   (View)

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HIGH_LEVEL_ACTIVATION_BY_CMOS

Published:2009/7/2 5:07:00 Author:May

High output of tpical CMOS gate drives complementary MPS-A13 Darlington transistor having80-mA lamp load.-A Pshaenich, InterfaceTechniques Between Industrial Logic and Power Devices,| Motorola,Phoenix,AZ,1975,AN-712A,p 11   (View)

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LOGIC_PROTECTOR

Published:2009/7/2 5:00:00 Author:May

Simple bidirectional triac crowbar can be set so positive voltages above 6 V and negative voltages greater than 1.5 V cannot reach digital logic. Article covers initialadjustment of R2、-D L,Spome,Bidirectional Crowbar Protects Logic,EDN Magazine．Dec15,1970,p37   (View)

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