دائرة الرنين الكهربي

LOW.


In a 'Schmitt trigger' circuit there are two different switching
thresholds. If Vin is slowly increased starting from 0 V, the output
voltage snaps from HIGH to LOW when Vin reaches a level equal to 2/3 of
the power supply voltage. Once this level has been exceeded, decreasing
Vin does not affect the output until Vin drops below 1/3 of the power
supply voltage. (If an input change in one direction produces a
different result from a change in the opposite direction, the circuit is
said to show hysteresis.)
If a filament lamp is connected between the positive power supply rail
and the output, as shown above, current flows through the lamp when the
output voltage is LOW. In other words, the lamp lights when the input
voltage is HIGH.
If you connect the lamp between the output and 0 V, the circuit will
still work, but the lamp will light when the input voltage is LOW:

Note that, in both versions of the circuit pins 2 and 6 are joined
together. The circuit can be simplified by omitting the 10 nF bypass
capacitor, and will continue to work when the RESET input, pin 4 is left
unconnected.
Some people are very fond of this circuit and use it whenever a
transducer driver is required. However, with a HIGH/LOW digital input
signal the same result can be achieved more obviously and at lower cost
using a transistor switch circuit



plitude in comparison with the sine and sawtooth waveforms. Check out the pictures below.

This is the top of the circuit board. I used some non-coppered
perfboard I had lying about to build the circuit on. Whenever I use
perfboard, I like to mark up my perfboard with some fine point Sharpie
markers and get all the connections worked out before I actually
construct the circuit.



I find it easier to do it this way. This is the back side. It's a little
more challenging using this type of perfboard over the copper padded
type.



Here is a view of the front. The enclosure comes from a defunct 4-way
data switch box. I gutted it and created some graphics for the
faceplate. It measures 7.5"x2.25"x5" deep. For the frequency range
switch, I used a recycled rotary switch from an old parallel port A/B
switch box. To make it work with this circuit, I had to disassemble it
and rearrange the insides a little bit, but now it does exactly what I
want it to. (I know, I could have just bought a new rotary switch, but I
had this switch lying around...) Since I am using a single female BNC
jack and a single 1/4" jack wired in parallel, I decided to use three
SPST switches to switch between the different waveforms. One of the
switches will be a on-center off-on type. I figure the middle position
would make a nice "kill switch" which will prevent any waveforms from
reaching the output jacks. I like the idea, because if I don't want any
output, I can just flip that switch and leave the unit powered up. Of
course, one could just use another rotary switch with a SPST switch that
could act as a kill switch as well. I used the SPST switches mainly
because I had a bunch of them lying around waiting for a new home...
This homebrew function generator isn't as fancy or accurate as the ones
that are on the market, but for a do-it-yourselfer hobbyist type, it's
adequate. I have found that the sine wave isn't totally accurate when I
switch between frequency ranges, but I have incorporated a pot which
corrects any waveform offsets, so it still quite useable and pretty
accurate. Not too bad for a $20 project.

Electronics -- ICL8038-based Oscillator

Overview

The circuit here presents an Oscillator featuring the following attributes:

* 1.1A guaranteed output current for sine and triangle waves with thermal shutdown and protection diodes
* Variable offset and gain for the sine/triangle output
* CMOS-compatible complementary square wave outputs capable of
driving into 50 Ohm with rise/fall times of 30ns at 10V (new in Rev 3).
* Frequency range 0.5Hz to 300 kHz (but signal degenerates when approaching the upper frequency limit)
* Single supply operation, 5V to 15V
* About 50% duty cycle (non-precision and adjustable via a trim pot)

(This is the 3rd revision dated 09/2004.)

Circuit

The circuit is a fairly easy design: It consists of the actual VCO
(ICL8038 with supplement parts), the sine and triangle output stage
(LT1210) and the CMOS-compatible output stage using the MOSFET driver
chip ICL7667.
Download function generator circuit schematic:
PNG image (854x734 as seen below): funcgen8038-rev3.png (26kb)
High-quality PDF: funcgen8038-rev3.pdf (162kb)
Permission to copy and use this schematic is hereby granted provided credit is given where it is due.

The ICL8038 and all parts around on the lower half of the sheet make up
the actual oscillator which is a modified design based on one of the
application examples in Intersil's data sheet. There is a large 6-stage
switch (S1) to select the major frequency and a logarithmic
potentiometer (R2) for minor frequency selection.
I discourage implementing the oscillator as shown in the above sheet
because most of the other potentiometers turned out to be without
significant enough effect on the output wave form to jusify their
application. Furthermore, duty cycle adjustment will not keep a 50%
ratio over all frequencies.
The switch S2 is used to choose between sine and triangle wave for the high-current amplifier.
The CD4030 on the left top is used as CMOS-logic signal preconditioning
feeding the MOSFET driver IC ICL7667 as output stage for the
complementary square wave output. The application of the two XOR gates
has the advantage that it can supply a sqare wave and its complement
without time offset between them (because CMOS has balanced raise and
fall times). Use a bypass capacitor near the ICL7667 device as it can
draw quite strong currents and is capable of driving into 50 Ohm up to
at least 10V resulting in rise/fall times of 30ns. So, I'm now entirely
satisfied with the digital output.
The industry-standard LM741 in combination with R11 is used to adjust
the sine/triangle offset level. (Hint: You should probably use something
better here - especially more output current cannot hurt.) Since this
oscillator is single-supply, it comes handy that you can change the
"zero level" of the wave output; you will normally adjust that to half
of the supply voltage. R11 is meant to be available to the user.
The actual sine/triangle output amplifier was a bit hard to find because
it should be able to drive 1A while still not degenerating signal wave
form at some hundred kHz. After some searching, I found the ADSL line
driver LT1210 from Linear Technology. Being an ADSL line driver, it has a
high GBP and high slew rate while providing the required output current
(1.1A guaranteed) at all frequencies in question. The part can be
obtained e.g. from Bürklin.
It turned out that this quick current feedback amplifier required very
good DC decoupling/bypassing capacitors in order not to start
oscillating of its own (at frequencies up to 40MHz). It took me a lot of
time to get it work properly; but once that is achieved, the amplifier
shows very good performance. (Note: The current implementation is not
yet perfect as I noted some months later: It may still start oscillating
for parts of the period when driving some special loads.)
R18 is used to trim the VCO output offset from the ICL8038 (about half
supply voltage). R12 is meant for the user as gain adjustment to tune
the sine/triangle amplitude from zero to more than supply voltage
(resulting in wave tips being cut off). The maximum gain is trimmed by
R13/R14 and care sould be taken to use proper values (consult LT1210's
data sheet for details).


http://www.intersil.com/cda/devicein...L8038%2C0.html


http://www.intersil.com/data/FN/FN2864.pdf

Function Generator

Notes:



Built around a single 8038 waveform generator IC, this circuit produces sine, square or

triangle waves from 20Hz to 200kHz in four switched ranges. There are
both high and low level outputs which may be adjusted with the level
control. This project makes a useful addition to any hobbyists workbench
as well.
Allof the waveform generation is produced by IC1. This versatile IC even
has a sweep input, but is not used in this circuit. The IC contains an
internal squarewave oscillator, the frequency of which is controlled by
timing capacitors C1 - C4 and the 10k potentiometer. The tolerance of
the capacitors should be 10% or better for stability. The squarewave is
differentiated to produce a triangular wave, which in turn is shaped to
produce a sine wave. All this is done internally, with a minimum of
external components. The purity of the sine wave is adjusted by the two
100k preset resistors.
The wave shape switch is a single pole 3 way rotary switch, the wiper
arm selects the wave shape and is connected to a 10k potentiometer which
controls the amplitude of all waveforms. IC2 is an LF351 op-amp wired
as a standard direct coupled non-inverting buffer, providing isolation
between the waveform generator, and also increasing output current. The
2.2k and 47 ohm resistors form the output attenuator. At the high
output, the maximum amplitude is about 8V pk-pk with the square wave.
The maximum for the triangle and sine waves is around 6V and 4V
respectively. The low amplitude controls is useful for testing
amplifiers, as amplitudes of 20mV and 50mV are easily achievable.
Setting Up:
The two 100k preset resistors adjust the purity of the sine wave. If
adjusted correctly, then the distortion amounts to less than 1%. The
output waveform ideally needs to be monitored with an oscilloscope, but
most people reading this will not have access to one. There is however,
an easy alternative:- Winscope. This piece of software uses your
soundcard and turns your computer into an oscilloscope. It even has
storage facility and a spectrum analyser, however it will only work up
to around 20KHz or so. Needless to say, this is more than adequate for
this circuit, as alignment on any range automatically aligns other
ranges as well. Winscope is available at my download page click here.
Winscope is freeware and designed by Konstantin Zeldovich. After
downloading, read the manual supplied with winscope and make up a lead
to your soundcard. My soundcard is a soundblaster with a stereo line
input, i made up a lead with both left and right inputs connected
together. Connect the lead to the high output of the function
genereator, set the output level to high, shape to sine, and use the 1k
to 10k range, (22nF capacitor). A waveform should be displayed, see the
Figure 1 below:-

Figure 1.
Here an undistorted sine wave is being displayed. The display on
winscope may flicker, this is normal as it uses your soundcard to take
samples of the input waveform. The "hold" button on winscope will
display a steady waveform.
Alignment:
First adjust the 100k preset connected to Pin 1 of the 8038. An incorrect setting will look similar to the waveform below:-


Adjust the preset so that the top of the sine wave has a nicely rounded
peak. Then adjust the other preset, again an incorrectly adjusted
waveform is shown below:


The two presets work together, so adjusting one affects the other. A
little is all that's needed. When your waveform is asjusted and looks
similar to Figure 1 press the FFT button on winscope. This will preform a
fast fourier transform and the displayed output will be a spectrogram
of the input. For a pure sine wave, only one signal is present, the
fundamental frequency, no harmonics will be present and so a spectrogram
for a pure sine should contain a single spike, see Figure 2 below:-

Figure 2.
A distorted sine wave will contain odd and even harmonics, and although
the shape of the sine may look good, the spectrogram will reveal spikes
at the hormonics, see below:-



Once alignment of the sine wave is complete, the other wave shapes will
also be set up correctly. Below is a picture of the triangle waveform
generated from my circuit:-


Finally the ICL8038PCD is available from Maplin Electronics order code YH38R.
Return to Test Gear

مشكورا انتظار تحميل كافة الصور فى كل المشاركات حتى يسهل الشرح الموجود وشكرا لكم
Electronics related projects, information, and resources.
20MHz High Speed Function Generator The High Speed Function Generator
was published in the professional electronics section of the Aug 1996
issue of Electronics Australia, and has proven to be extremely popular.
The kit is no longer available from any of the kit suppliers.
The project is capable of generating 20MHz or greater Sine, Square, Triangle, and TTL waveforms.


The finished HSFG project, as published.
Read the complete article 20Mhz Function Generator
View the Schematic Diagram.
View the PCB for the published version in 300dpi GIF format
View the PCB for the simpler PCB mount version in 300dpi GIF format.

My first HSFG prototype.
A double sided board with everything PCB mounted.
YES, those electro's are hanging over the edge of the PCB. I didn't have
anything else available, and Jaycar was closed !. This one didn't have
the TTL output, that was a last minute inclusion in the second prototype
that was published, hence the oversight described below.
Notes & Errata
There is a problem with the TTL output when the generator is used on the
LOW and MEDIUM frequency ranges AND the MAIN frequency adjust control
is set to the lower 15% of it's range. Any significant loading on the
TTL output will cause it to osscillate on the positive and negative
edges. This is apparently an inherent problem with the MAX038 chip !.
The only solution is to buffer the SYNC output of the MAX038 with a
74HC14 schmitt inverter. This can be mounted on a small piece of
vero-board along with R10 and a bypass capacitor. Use the other 5
inverters in the package in parallel to provide a high current buffered
output. Be sure to connect the supply pins of the 74HC14 directly to
pins 15 and 16 of the MAX038.

I attached a pic showing three different dave lawton circuit schematics.
My question is, which one to use!!! Each one has minor differences from
the other two. I am still building my skill in circuit construction, so
I don't want to have to guess if the circuit I am trying to build even
works. Any help on which circuit (which D14.pdf version) to use would be
great. I know there was another posting on this, but no one has posted a
pic showing the three different versions. Thanks.


D14 Version Comparison.JPG De******ion: These schematics are of the
following dates: June 2nd, June 10th, and December 24th Filesize: 181.98
KB Viewed: 159 Time(s





w if there is anything I can inprove..
Thanks..


b2_spice_dave_lawton_circuit_picture_293.JPG De******ion:
Filesize: 198.73 KB Viewed: 668 Time(s)




Dave Lawton PWM B2 spice v5 with VIC.txt De******ion:

Download Filename: Dave Lawton PWM B2 spice v5 with VIC.txt Filesize: 280.28 KB Downloaded: 88 Time(s)

total uninstall installation.txt De******ion:

Download Filename: total uninstall installation.txt Filesize: 822.6 KB Downloaded: 68 Time(s)


Last edited by eclipsed78 on Sun Sep 16, 2007 12:20 pm; edited 3 times in total

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Rb and Ct with the controls given and see the change of frequency, period and duty cycle.

Astable 555 Multivibrator - doc00019
The Interactive demo below requires images and java****** to be enabled.
freq Hz period Sec duty cycle
Power