Clock oscillators are circuits which generate square wave or nearly
square wave signals suitable for digital electronics circuit as clock signal. The most
common simple clock oscillator types are resistor-capacitor (RC) and inductor-capacitor
(LC) oscillators.
CMOS
Oscillator - 4 MHz oscillator using 74HC14 and inductor
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 are oscillators where the primary frequency
determining element is a quartz crystal. Because of the inherent characteristics of the
quartz crystal the crystal oscillator may be held to extreme accuracy of frequency
stability. Crystal oscillators are usually, fixed frequency oscillators where stability
and accuracy are the primary considerations. Temperature compensation may be applied to
crystal oscillators to improve thermal stability of the crystal oscillator.
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
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
Sine wave oscillators are useful in applications like audio signal
generation, reference signals for different applications and in measurement applications.
1 kHz
Audio Oscillator - This circuit consists of a CMOS square wave oscillator on a
frequency of approximately 1 kHz. The RC filter, which has a roll-off frequency of 500 Hz,
filters the harmonics, providing a sine-wave output. The oscillator has many uses,
sidetone circuits in transmitters and signal injectors for audio tests are just two.
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
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
Microcontroller
emulates numerically controlled oscillator - Microcontrollers commonly add
intelligence or digital functions to products, but they can also provide a variety of
analog signals. An 18-pin PIC 16C54 microcontroller, combined with an inexpensive, 8-bit
DAC and a simple lowpass filter, can generate sine waves from dc to approximately 50 kHz
with a tuning resolution of 24 bits.
Programmable
oscillator uses digital potentiometers - This Design Idea describes an oscillator in
which setting the resistance of two digital potentiometers independently programs the
oscillation amplitude and frequency. This design idea uses diode-stabilized Wien-bridge
oscillator that generates accurate sine waves from 10 to 200 kHz.
Sine
reference is synchronous with ac line - Many applications require a sinusoidal
reference voltage synchronized to the ac line voltage. You cannot derive such a reference
voltage directly from the ac line because the waveform of the ac line is distorted because
of nonlinear loads connected to the line and because the amplitude of the line signal
varies.
Clock
Generators - crystal oscillators for 20 MHz and 3.5795 MHz
Digital
Clock Circuit - This circuit provides a digital square wave that can be viewed
directly or used to drive other circuits. It uses the CMOS 4047 Low-Power
Monostable/Astable Multivibrator.
Inverters
form three-phase VCO - You sometimes need an inexpensive VCO that can produce evenly
spaced three-phase outputs over a wide frequency range. This application uses unbuffered
U-type inverters for use in ring oscillator setup which generates relatively squarish
somewhat sine-like waveforms. The range of frequencies over which the circuit can operate
is more than 1000-to-1.
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.
Use
printer port as programmable frequency generator - A simple and inexpensive circuit
and a simple C program are all you need to turn your PC's printer port into a programmable
frequency generator. Using a few low-cost and readily available components, the circuit
occupies little space and is easily attachable to the printer port. With this circuit you
need only enter the desired frequency, and the PC does the rest. The circuit uses a
MAX5130 low-power, programmable, 13-bit DAC, IC1; an OP07 buffer; and an AD537 VFC
(voltage-to-frequency converter). The PC controls the DAC using a three-wire serial
interface.
The Pulse Width Modulator (PWM) is a very useful circuit that
outputs a variable duty cycle at a fixed frequency (duty cycle is usually controlled using
external control signal, potentiometer or using numerical control). The PWM is very useful
in applications like wave generation, motor control and DC power controlling systems. With
the aid of a filter, smooth analog waves can be generated usign PWM method.
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
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.
Function Generator
- Built around a single 8038 waveform generator IC, this circuit produces sine, square or
triangle waves from 20Hz to 200kHz in four switched ranges.
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
Scheme
yields frequency-locked triangle waves - circuit generates frequency-locked triangle
waves of constant amplitude, uses readily available TTL and other older-technology parts
SCR Oscillator -
Silicon controlled rectifiers (SCR) can easily oscillate if there is an inductor (a
speaker coil in this case) which gives just enough extra voltage to completely switch off
the sustain current. In this way a new cycle may start and oscillations set in. It
operates over a wide range of supply voltage and components values are not critical at
all. Operational frequency in this circuit goes from 100Hz at 11V to 10KHz at 100V.
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
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
Zener Oscillators
- These two circuits are interesting from an academic point of view. Their practical
implementation is rather critical and it is not easy to get steady operation.
Multivibrators are circuit which change their state contantly
between different states (usually two states) at predefined rate. Multivibrators are
usually used to generate square wave clock signals, but they can be used also for other
applications.
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
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
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
Noise generators are generally used in various measurements. The
most common way to generate noise signals are to use a randon-bit-sequence generator or to
amplify the thermal noise of some electronic component (usually diode or transistor). The
most commonly needed noise sources in audio measurements are "white noise" and
"pink noise". White noise is pure random noise, and the pink noise is
specifically filtered white noise. In some digital telecommunication testing applications
streams of random or semi-random bitstreans are needed. Those random or semi-random
bitstreams are generated using a random-bit-sequence generator.
Audio
Frequency Digital Noide Generator - When you need to test an audio circuit with
broadband noise, this circuit works great. It uses just three inexpensive C-MOS ICs that
generate a series of output pulses whose widths vary randomly. This circuit includes a
level control pot. The circuit is in pdf format.
Circuit
forms random-bit-sequence generator - A random-bit-sequence generator is basic
equipment for prototyping and testing any data-transmission system. You use such a
generator when measuring BER (bit-error rate) and pattern-dependent effects in a
transmission system.
Noise Generator -
Sometimes there is a need for a noise generator: this will work well in the audio range
and, without the 680pF capacitor, will extend in the radio frequency range up to 20-30MHz.
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
Single
IC forms pseudorandom-noise source - Trying to find a single IC noise source can be
frustrating. You could use a single-chip microcontroller, such as Microchip's 12C508 for
this application. This article gives you idea and software how to do that.
A voltage controlled oscillator or as more commonly known, a VCO, is
an oscillator where the control voltage controls the oscillator output frequency. VCO can
be built using many circuit techniques. For RF applications the principal variable or
tuning element is a varactor diode. This kind of RF voltage controlled oscillator is tuned
across its band by a "clean" dc voltage applied to the varactor diode to vary
the net capacitance applied to the tuned circuit.
Phase locked loop (PLL) is a system which consists of a voltage
controlled oscillator, phase comparator and feedback circuit. PLL it's basic form takes in
a reference frequency and tries to output the same frequency out (with a known phase
shift). With a feedback circuit which contains a frequency divider it is possible to
generate output frequencies which are N times the input frequency.
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
Software PLL
locks VCXO to reference - provides a precisely controlled clock signal using voltage
controlled crystal oscillator controlled by microcontroller
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
Delay
line aids in one-shot simulations - Many designers use small pulse generators to delay
signals, open timing windows, drive sample/hold circuits, and other functions. Though the
hardware implementation of these generators does not pose any problems, the lack of
dedicated circuitry sometimes puzzles the Spice simulation of the system.
High-speed
pulse generator has programmable levels - This circuit can create fast rise time
pulses whose high and low levels are programmable. Signal rise times in nanoseconds range.
Pulse rate can be controlled with external circuit.
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
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
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 are circuit which are trigged by input pulses. When
they are triggered, they will wait for a predetermined time to change the output state.
The most commonly used timer circuits are monostable multivibrators and time delay
circuits. A time delay circuit works so that when the input comes active, the output gets
activated after a predetermined time. A monostable multivibrator works so that a trigger
pulse actives it, the output turns active. After a predetermined time the monostable
circuit deactivates itself and the output.
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
Long Delay Timer
- A max. delay of 20 hours is achieved by this relatively simple circuit.
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
The watchdog circuits used with microcontrollers are usually built
in such way that the software running in the microcontroller periodically resets the
watchdog circuit. If no watchdog circuit "reset" signal is received during a
predetermined timeframe, the watchog circuit will activate it's alarm output (which is
usually used to reset the microcontroller circuit to start all over). Watchdog circuit
then causes an alarm when the software crashed (whn software crashes, it does not anymore
give out watchdog reset pulses).
Circuit
makes simple FSK modulator - The need for a compact telemetry system poses a challenge
for designing a small, light, low-component-count system. Commercial FSK
(frequency-shift-keying) modulators are bulky and need many passive components. This
circuit uses a single NOT gate (inverter), an On Semiconductor NL27WZ14 in a surface-mount
package, to generate continuous FSK data from TTL-level signals. This circuit is designed
to provide 2400 Hz / 1200 Hz FSK, but can be adapted for other frequencies up to an
operating frequency of approximately 80 kHz.
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
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
Slew
Rate Control - A circuit that limits the rate of change of a signal; a feature of this
design is that the positive and negative rates can be different.
Watchdog
circuit uses ac triggering - A dc-triggered reset of a watchdog circuit is prone to
failure. If the watchdog program hangs up, then the reset signal becomes activated
continuously, and the microprocessor has no way to escape the situation. This simple
solution uses an ac trigger to reset the watchdog circuit.
