Unusual functions of cheap parts
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From: Henry Kiefer on 26 Nov 2005 18:06 That is not new to me but thanks! Is the oscillator useful at 150MegHz? Modulable? Maybe I can make transmitter... Tell us more, please. cu - Henry "wa2mze(spamless)" <"wa2mze(spamless)"@bellsouth.net> schrieb im Newsbeitrag news:tT_hf.27576$s92.24482(a)bignews6.bellsouth.net... > Henry Kiefer wrote: > > Hi all - > > > > After my first thread going from "standard" cheap parts for up to vhf > > frequency to a discussion about the usefulness of Spice simulator...... I > > try it another time hopefully get attention of frustrated co-readers: > > > > For example the rechtifier diode 1N4007 can be used as a rf switching diode, > > for example as rx/tx-switch. This is because it is a pin structure diode. > > This type is cheap and you can get it almost everywhere. It shows good > > performance for the price. Surely for high-end you should do it with another > > type tuned to the application it is made for. But anyway it works in some > > circuits. > > > > Do you know of other interesting devices or circuits good for misuse? > > > > Best regards - > > Henry > > > > > Take one P channel Jfet and one N channel Jfet and connect them > in series so the two sources are together, connect the gate of > each transistor to the other one's drain. This is known as a lambda > connection, and if you plot the voltage vs current from drain to drain > you will see a negative resistance region, usually around 3v > (depending on the transistors). The circuit will work as a tunnel > diode oscillator up to 100-200mhz.
From: Henry Kiefer on 26 Nov 2005 18:08 Don't forget the LED as an low-noise zener diode with integrated function control. Some high-fidelity enthusiasts use this in good audio amplifiers. - Henry "ehsjr" <ehsjr(a)bellatlantic.net> schrieb im Newsbeitrag news:R3thf.9922$BU2.983(a)trndny01... > Henry Kiefer wrote: > > Hi all - > > > > After my first thread going from "standard" cheap parts for up to vhf > > frequency to a discussion about the usefulness of Spice simulator...... I > > try it another time hopefully get attention of frustrated co-readers: > > > > For example the rechtifier diode 1N4007 can be used as a rf switching diode, > > for example as rx/tx-switch. This is because it is a pin structure diode. > > This type is cheap and you can get it almost everywhere. It shows good > > performance for the price. Surely for high-end you should do it with another > > type tuned to the application it is made for. But anyway it works in some > > circuits. > > > > Do you know of other interesting devices or circuits good for misuse? > > > > Best regards - > > Henry > > > > > > An LED as a shunt regulator. Also, as a varicap. > Ed
From: John Larkin on 26 Nov 2005 18:41 On Fri, 25 Nov 2005 10:52:26 +0100, "Frithiof Andreas Jensen" <frithiof.jensen(a)die_spammer_die.ericsson.com> wrote: > >"Henry Kiefer" <otc_friend(a)gmx.net> wrote in message >news:4385b3b1$1$27887$9b4e6d93(a)newsread4.arcor-online.net... > >> Do you know of other interesting devices or circuits good for misuse? > >LED's work both ways, as a light emitter and a photodiode. > And optocouplers can do interesting things: Very simple high-voltage opamp, up to 400 volts p-p. Isolated totem-pole driver, from a few volts up to 400. Current limiter. Low-leakage diode, sort of like an LED painted black. John
From: Ken Smith on 26 Nov 2005 18:51 In article <4388f068$1$27889$9b4e6d93(a)newsread4.arcor-online.net>, Henry Kiefer <otc_friend(a)gmx.net> wrote: >Don't forget the LED as an low-noise zener diode with integrated function >control. Some high-fidelity enthusiasts use this in good audio amplifiers. It also works for this: Vcc !/c --/\/\/\---+------! ! !\e V ! --- ----/\/\/--+--- too load ! ! -------------------- You get a current limit and an indicator light. -- -- kensmith(a)rahul.net forging knowledge
From: Henry Kiefer on 26 Nov 2005 18:39
Bob Pease of National Semi mentioned a ONE AND ONLY transistor circuit above/under voltage rail converter (with detailed theory). I cannot remember the details. But interesting if sometime a slightly voltage behind the power rail is needed. For example to power a CMOS Opamp now doing rail-input. - Henry |