Oscillator circuits

General

• Clock Oscillator Basics
• Rules of thumb aid in time-constant analysis - information on calculating time constands on RC circuits

RC and LC clock oscillators

• CMOS Oscillator - 4 MHz oscillator using 74HC14 and inductor
• CMOS inverter VCO tunes octave to UHF - robust and versatile vco provides a stable output to 300 MHz
• CMOS RC circuits - includes CMOS 555 timer clock oscillator and schmitt-trigger RC oscillator
• Crystal 32.768KHz CMOS Oscillator
• Sqaure Wave Oscillator - two gates from a CMOS 4011 NAND chip form a simpel square wave oscillator where the mark space ratio can also be independantly controlled by varying the value of the resistors

Crystal oscillators

General information

• 10 Quick Tips for VCXO Specifications
• High system speeds are making clock design a critical problem - Clock signals distributed within a printed-circuit board andaround a system must be clean, stable, synchronized, and have as near toa 50:50 duty cycle as possible

Desing articles

• Circuit Techniques for Clock Sources - pdf file with many circuit examples
• Crystal oscillators: looking good in wireless systems - with the assistance of stabilization and tuning tricks, crystals makes an ideal frequency reference for wireless systems
• Design Of A Low-Power Crystal Oscillator
• Oscillators for microcontrollers - lots of information on crystal oscillator design, 40 pages pdf document, 900 kilobytes in size

Circuits

• 2 MHz Oscillator
• 50 - 150MHz Overtone Oscillator
• Crystal 32.768KHz CMOS Oscillator
• Crystal Oscillator - from 1 MHz to 40 MHz using CMOS or HCMOS inverter
• Oscillator lowers distortion and phase noise - this low-distortion crystal oscillator is essentially a modified Clapp oscillator that uses a four-transistor voltage follower instead of a single transistor and connects the crystal to a virtual ground at node G
• Crystal oscillator overcomes typical drawbacks - drive heavy loads, the duty cycle is adjustable from 25 to 75%; and feedback minimizes the drift
• Precision 1Hz Clock Generator using Chip-on-Board - circuit for generation of 1Hz clock for applications for application where good accuracy is needed, uses chip-on-board (COB) device found inside a digital clock which is readily available in the market
• Very low power gated crystal oscillator - continuously operating 32KHz crystal oscillator to the input of a C-MOS buffer when clock pulses are needed, standby power consumption to a very low 1uA when used with a 3v supply, pdf file

Sinewave oscillators

• 68HC11 synthesizes accurate sine wave - you can use a 68HC11 and a 12-bit serial DAC to generate accurate sine waves without using floating-point arithmetic
• Amplitude-stable oscillator has low distortion, low cost - square wave and sinewave oscillator examples
• Audio signal (sinewave) generators - wien bridge oscillators, twin-t network oscillator and RC phase shift oscillator
• Audio Test Oscillator - Wein Bridge Basic Circuit
• Current-feedback amp yields simple oscillator - handful of components configures a current-feedback op amp as a large-amplitude sine-wave oscillator with independent adjustment of amplitude and frequency
• Digital signals produce pure sine waves
• Gates provide low-cost sine-wave generator - simple device to generate 300 to 4000 Hz test signals
• Op-amp oscillators simplify RF designs - a novel circuit that uses a low-cost, high-speed op amp as a crystal-controlled RF sine-wave oscillator
• Simple circuit generates clean sine waves - technique for generating a high-quality sine wave from a square-wave source
• Voltage controls sine-wave frequency - generates a 50-Hz to 1-kHz sinusoidal waveform that exhibits lower than 60-dB THD

Square wave oscillators

• 200-400MHz voltage controlled oscillator - produces clean emitter coupled logic (ECL) type signal between 200MHz and 400MHz, pdf file
• 555 Tone Generator for 8 ohm speaker - used to produce a 1 Khz tone from an 8 ohm speaker
• Amplitude-stable oscillator has low distortion, low cost - square wave and sinewave oscillator examples
• Generator has independent pulse width and frequency adjustments - modified 555 based circuit
• Low frequeny oscillator draws only 500 nanoamperes - circuit draws only 0.5 microamps from a 6 volt supply, outpur frequency is 2 Hz but can be tuned up to 300 Hz, based on CD4007UB IC
• Multivibrators, relaxation oscillators and their allies - astable multivibrator, asymetrical multivibrator, complementary multivibrator, series multivibrator, emitter coupled multivibrator and more
• Precision ultra low power oscillator - works much like the classic 555 timer, but draws only about 1.5 microamps from a 3 volt battery, highly stable under varying temperature and supply voltages, pdf file
• Programmable Clock Oscillator - voltage controller oscillator that was designed as a wide range oscillator to generate clock pulses for a stepper motor drive system, frequency could be varied over 1,000,000:1
• Simple Square Wave Oscillator - This simple kit, based on the popular 555 timer IC, generates six preset frequencies - 1Hz, 10Hz, 100Hz, 1KHz, 10KHz and 100KHz. The output is selected by setting a jumper position. It has a wide operating voltage (5-18V) and even provides visual indication (LED) of the output.
• Small tone generator - powered it with two 3 V lithium button cells and powers a small 0.25W speaker
• Variable Mark/Space Oscillator with Complimentary Outputs

Pulse Width Modulation

• Circuits provide 4- to 20-mA PWM control - are useful when you use 4- to 20-mA current-loop signals to control a PWM signal
• Generator features programmable duty cycle - you can program the duty cycle of this simple pulse generator's output
• Pulse Width Modulators - generating PWM waveform is extremely simple with the circuits shown in this page, all circuits are DC control voltage in and PWM out
• PWM circuit uses one op amp - circuit delivers a rectangular signal with duty cycle varying between 0 and 100% in response to an input signal varying from 0 to 5V dc

Oscillators with other waveforms

• 20MHz Function Generator - This compact function generator provides sine, square and triangular waveforms up to 20MHz over three ranges using "course" and "fine" frequency adjustment controls. The output level is adjustable from 0 to 2Vp-p. A TTL output is also provided for connection to a frequency counter.
• Générateur de fonction 0.1 Hz - 10 Mhz - funacion generator 0.1 Hz - 10 MHz, based on MAX038, text in French
• Low Cost Function Generator - low-cost function generator, based on the Maxim MAX038 high-frequency waveform generator, produces sine, triangle, and square waves from under 1 Hz to over 20 MHz
• Oscillators convert temperature to time - simple arrangement of active-R oscillators can generate an excellent triangular waveform
• Programmable ramp generator has 14-bit linearity - this linear ramp generator uses a DAC, a transistor array, MOSFET switches, and current-steering techniques to achieve 14-bit linearity
• Scheme yields frequency-locked triangle waves - circuit generates frequency-locked triangle waves of constant amplitude, uses readily available TTL and other older-technology parts
• Summer linearizes ramp and triangle generators - op-amp adder that sums a reference voltage with the voltage on C1 allows the ramp generator and the triangle-wave generator to charge capacitor linearly
• Transistor Organ - very simple electronic instrument
• Triangle and Squarewave Generator - uses common 1458 dual op-amp
• Tri-Waveform Generator - signal generator to test circuits, frequecy range is 20 to 20 kHz, outpus sinewave, triangle wave and square wave
• Versatile Waveform Generator Operates from 0.1Hz to 20MHz - a single-chip source of high-frequency waveforms, the MAX038 can serve both as the core of a moderate-performance waveform generator, and as a card-level waveform source for electronic systems
• Waveform Conversions: Sine to Square and Square to Sine
• Waveform generator circuits - ramp generator, phase oscillator, quadrature sine/cosine oscillator

Multivibrators

• Circuit forms clockless, programmable one-shot - replace the timing resistor on a 74LS123 one-shot with a Howland current pump, drive the pump with a rail-to-rail voltage-output DAC, and you have a programmable one-shot with some unique features: single-supply operation, no clock required, a 25-to-1 pulse with adjustment range, and an "infinite" pulse-width capability
• D-flip/flop one shot circuits - you can use cheap D flip/flop logic circuits as nice one-shot pulse generators, this circuit shows how the popular CD4013 and the CD74HC74 can be used to generate pulses ranging from nanoseconds to seconds, pdf file
• LM555 timer chip datasheet - very popular timing IC used for monostable multivibrators and oscillators
• Basic IC MonoStable Multivibrator
• CMOS RC circuits - oscillator, one-shot and button debounche
• Discrete Multivibrator Schematic - astable multivibrator using discrete parts
• Long period computer watch dog timer - simple 4060 IC oscillator/timer which is reset periodically by a computer. Should the computer fail to send a pulse, the output changes state, time can easily be set from seconds to hours, pdf file
• Simple monovibrator uses three PLD pins - if you can afford just three spare PLD pins, this circuit is an alternative to using yet another 555
• Slow op amp makes fast multivibrator - improved version of classic one-shot multivibrator using an op amp, example circuit generates a pulse of approximately 700-µsec width with a 5-nsec, 2V triggering pulse
• Switch De-bouncer Using a 555

Flashing circuits

• Basic LM3909 Led Flasher - runs from 1.5V battery
• LED flasher - makes two LEDs alternately flash, two circuit examples

Noise generators

• Hardware Random Bit Generator
• Pseudonoise generator doubles its speed - you can double the speed of a standard pseudonoise (PN) generator by using additional exclusive-OR gates and a fast 2:1 multiplexer
• Random Noise Sources - Producing crypto-quality randomness in a computer is a perennial issue in cryptography, here are some ideas

Phase locked loops

• Inverting latches make simple VCO - simple VCO circuit which is synthesized from inverting latch stages and is tunable to an integer multiple of the input frequency by selecting which output phases feed back to the input multiplexer, suitable to be usable as on-chip clock multiplication in ASICs
• Low-cost circuit biases VCOs for cable and TV - PLLs are useful in a variety of applications, most notably cable and TV tuners
• Software PLL locks VCXO to reference - provides a precisely controlled clock signal using voltage controlled crystal oscillator controlled by microcontroller
• Straightforward techniques cut jitter in PLL-based clock drivers - this article describes jitter and its causes and effects and shows you how to reduce it
• Synchronous oscillator outperforms the PLL - PLL has numerous limitations, including low input-signal sensitivity and contradictory design requirements, synchronous oscillator doesn't suffer from these problems and has many powerful properties
• Technique eases design of high-order PLLs - maintaining stability in high-order PLLs can be a chore unless you know exactly what you are doing

Pulse circuits

• CMOS buffer delivers precise current pulses - this circuit delivers stable, fast-settling reference-current pulses
• Micropower pulse generator - produces clean 2mS logic pulses at rate of one per second while drawing only 1 microamp from a 9 volt battery, uses 2 transistor acting as programmable unijunction transistor, pdf file
• One-shot remembers input-pulse width
• Pulse discriminator excises narrow pulses - circuit deletes narrow pulses from fixed-frequency PWM waveforms
• Pulse-width trimmer outdoes one-shots - trims the trailing portion of a large-width input pulse to a size as narrow as 10 nsec irrespective of the input-pulse width, circuit doesn't require a capacitor to generate the timing pulse
• Repeating one-shot yields clean, stable pulses
• Time Domain Reflectometer (TDR) - produces very sharp pulses in range of 10 ns to 5 us
• µC squares input signal - converting a random-width pulse to a signal with the same frequency but with a 50% duty cycle isn't easy but a small microcontroller can do it

Timer circuits

• A Technique For Forming Long Time-Constants
• Dual timer circuit with pulsed and constant outputscircuit consists of two NE555 timer IC's, one configured for monostable operation, the other for astable operation
• LM555 timer chip datasheet - very popular timer IC for all kinds of applications, check also 555 Timer Design Tool
• Logic IC yields simple, wide-range timer - you can use a 4060B binary counter/oscillator to make a simple, accurate, long-delay timer for times between milliseconds and hours
• One-shot circuit is programmable - digitally program the on-time of a one-shot multivibrator circuit based on NE555 timer and AD7524 DAC
• Simple timer exploits op-amp bias current - simple, low-cost analog timer exploits the parasitic input-bias current of op-amp to achieve long time delays even though it uses only low-value, inexpensive ceramic chip capacitors
• Timer provides power-off function - an interval from seconds to several minutes for automatic power-off switching in idle battery-powered systems
• µC-based one-shot has wide range - µC-based, digitally programmable, monostable multivibrator based on PIC16C54

Watchdog circuits for microcontroller and computer systems

• Universal watchdog fully controls µ Preset
• Watchdog circuit uses leftover gates - extremely simple watchdog circuti to be used with microcontrollers
• Watchdog timer reboots PCs - watchdog timer reboot the computer if it runs astray, uses a PIC16C84 µC to provide the watchdog function

Other related circuits

• 300V peak-to-peak signal generator - converts a square wave signal to a +-150 volt output signal with fast 100nS rise and fall times, pdf file
• Delay line implements clock doubler - using a 5-nsec delay unit, a 50- MHz, 50% duty-cycle square-wave input produces a 100-MHz, 50% duty-cycle output clock
• Frequency doubler operates on triangle waves
• Line powered 60 Hz clock generator - optosolated circuit is connected to the 120vac power line and transfers 60Hz clock pulses to a logic circuit, provides 5000V isolation from line, pdf file
• Negatrons enrich filter, oscillator designs - atest wave of high-performance op amps allows you to incorporate "negatrons" (synthesized negative resistors) into your oscillators and filters
• PSpice tunes oscillator circuits - optimization technique to determine the impedance, ZB, that compensates for parasitic phase shifts that the real amplifier introduces in this high-frequency oscillator
• Ring oscillator measures cable length - ECL exclusive-NOR gate (F100107) and a length of cable form a simple ring oscillator, the delay from the cable and the gate determine the ring oscillators frequency, 100m cable yields approximately a 1 MHz oscillation frequency
• Self-powered Sine to Square wave Converter - Converts sine to square waves without a power-source