+++++++++++++++++++ Date: Mon, 13 May 2002 22:58:28 -0400 From: "Mark J. Dulcey" To: henryf at quartz.gly.fsu.edu Cc: Low Power Amateur Radio Discussion Subject: [126635] Re: Diode Specs Henry Freedenberg wrote: > Ok > > Here is a really naive question: > > Are the 1n34, 1n914 and 1n4001 interchangeable? Why or Why not (25 words or > less) In a word, no. Each occupies a different ecological niche. The 1N34 is a germanium diode. As such, it has a low forward voltage drop, so it's good for detector circuits, especially when used without an amplifier (crystal set, SWR bridge). But it has high reverse leakage, and can't handle much current. The 1N914 is a small-signal silicon diode. It's useful when you need rectification, but don't have much current to handle - 100ma or so is about the most you usually want to push through one. (It can handle more than the 1N34, though.) It can be used in detector circuits when you have an amplifier in front of it. The 1N4001 is a medium-current silicon diode rated for a peak reverse voltage (abbreviated PIV, the I being "inverse") of 50 volts and a current of 1 amp. It's useful in power supply circuits. If the diode is going to see more than 25 volts, it's safer to use one of its higher-voltage relatives, the 1N4002 through 1N4007. The 1N4007, by the way, is also sometimes used as a poor man's PIN diode; in other words, as a diode switch. Even if the voltage in the circuit is low, as it often is, the lower-voltage relatives can't be used as substitutes; the 1N4007 is made differently, and works better in that application than the others do. +++++++++++++++ Date: Mon, 13 May 2002 22:55:26 -0400 From: David Hinerman To: qrp-l at lehigh.edu Subject: [126636] Re: Diode Specs Henry, No, they aren't interchangeable. The 1N34 is a germanium small-signal diode. It has a low forward voltage drop (about 0.3 V), low current capacity (about 150 mA, or so I've heard), relatively high reverse current, and high internal resistance. About its only "advantage" is the low forward drop. It can switch from "on" to "off" quickly when voltage is reversed, making it good for RF applications. The 1N914 is a silicon small-signal diode. It has a higher forward voltage drop (about 0.7 volts), moderate current capacity (a few hundred mA), low reverse curent, fairly low internal resistance. It can switch from "on" to "off" when voltage is reversed very quickly, making it good for RF and digital switching applications. The 1N4001 is a silicon power diode. It has almost the same forward voltage drop as the 1N914, high current capacity (2.5A comes to mind), low reverse current, and fairly low internal resistance. It doesn't switch as quickly as the 1N914, so it's a poor choice for RF use. Dave P.S. No charge for the extra words. (grin) D. At 10:11 PM 5/13/02 -0400, you wrote: >Ok > >Here is a really naive question: > >Are the 1n34, 1n914 and 1n4001 interchangeable? Why or Why not (25 words or >less) > >Henry ++++++++++++++++++ Date: Mon, 13 May 2002 23:15:20 -0400 From: "Mike Yetsko" To: , "Low Power Amateur Radio Discussion" Subject: [126638] Re: Diode Specs ----- Original Message ----- From: "Mark J. Dulcey" > The 1N4001 is a medium-current silicon diode rated for a peak reverse > voltage (abbreviated PIV, the I being "inverse") of 50 volts and a > current of 1 amp. It's useful in power supply circuits. If the diode is > going to see more than 25 volts, it's safer to use one of its > higher-voltage relatives, the 1N4002 through 1N4007. Ah, but the reason usually isn't the diode, it's the circuit. Too many people forget to figure the total reverse voltage applied in power rectifier circuits. If you have a diode, it doesn't just see the voltage at the output in reverse to 0, it sees the voltage on it's output in reverse to the SWING of the AC applied to the diode from the AC in the OTHER direction! You have to figure the voltage on the 'DC' side of the diode as if it were charged to peak max with no load, and you have to figure the voltage on the AC circuit as the PEAK voltage at the OPPOSITE peak of the AC waveform. If this can cause breakdown of the diode, things can go real bad real quick! I used to use the 1N4007 all the time, as if I remember they were the 1000v and 2.5A versions. Available for less money and three to a card at Radio Shack than the 1N4001/2/3/4 diodes at 2 to a card. (the 1/2/3/4 voltages were I seem to recall 50v, 100v, 200v, and 400v) I thought the 1N4007 would be a do all wonder. However, it has other issues... I haven't used one in maybe 15 years, but I seem to recall one of the issues was the time it takes from conduction to off. If it was forward biased, and you reversed the voltage, it would conduct for a relatively LONG time till it shut off in reverse. Much longer than the 1N4001-4 diodes. They got hot real quick. And if you waveform wasn't a nice pure sine wave, they would really heat fast! And usually trash. Mike +++++++++++++++++++ Date: Tue, 14 May 2002 07:27:34 -0700 From: Tayloe Dan-P26412 To: "'qrp-l at Lehigh.EDU'" Subject: [126655] Re: Diode Specs > >Here is a really naive question: >Are the 1n34, 1n914 and 1n4001 interchangeable? Why or Why not (25 words or >less) >Henry In addition to what has been already said, power diodes have lots of internal "C" compared to their "small signal" variations. In general, the extra "C" tends to make these diodes perform poorly (if at all) for RF purposes. Power diodes (1N4001 silicon, 1N5819 Schottky) are normally designed for lower frequency power supplies. Small signal diodes (1N914 silicon, 1N34 germanium, SD101 Schottky) have very little junction "C" and thus are useful in "small signal" high frequency RF applications. - Dan Tayloe, N7VE; Phoenix, Az; Az ScQRPions ++++++++++++++++