Maintaining a Vbe Multiplier's bias value
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From: Ban on 9 Feb 2010 17:38 "Jon Kirwan" <jonk(a)infinitefactors.org> schrieb im Newsbeitrag news:8te2n5llb72tgv03g653ajqjf360m3mc06(a)4ax.com... > On Mon, 8 Feb 2010 18:23:16 -0800 (PST), "miso(a)sushi.com" > <miso(a)sushi.com> wrote: > >><> > Okay. I'll do that if folks here aren't interested at all in > talking about it. > BS, a couple of good answers have come. Jon, you should read this book, bit torrentwise Audio Power Amplifier Design Handbook, 4th Ed. - (Malestrom) by Doug Self, one of the deeper going but still very practical publications, you'll love it. Ban
From: Jim Thompson on 9 Feb 2010 17:42 On Tue, 09 Feb 2010 14:30:54 -0800, Jon Kirwan <jonk(a)infinitefactors.org> wrote: >On Tue, 9 Feb 2010 15:48:42 -0600, "Tim Williams" ><tmoranwms(a)charter.net> wrote: > >>"Bob Monsen" <rcmonsen(a)gmail.com> wrote in message >>news:1265746051.657782(a)sj-nntpcache-3.cisco.com... >>> On a related note, there was an article in a recent EDN about a self >>> biasing preamp which was kinda cool. Instead of trying to track the >>> difference using diodes or a multiplier, it used a couple of transistors >>> and an opamp to set the correct values at the bases of the pass >>> transistors. It was so novel (at least to me) that I typed it into >>> LTSpice. Here it is: >> >>Could you take a screenshot of the schematic? > >I'll include an ASCII version here: > >>: R2 >>: +V = 12V ,------/\/\---------------------, >>: | 1k | >>: | +V | >>: | | | >>: | \ | >>: | / R1 | >>: | \ 1k5 | >>: | / | >>: | | +V | >>: C2 | ,----+ | | >>: || 10uF R4 | | | 2N3904| | >>: ,------||------/\/\---------+ | | | | >>: I| || 100 | | Q4 e>| |/c Q3 | >>: N| | | |-------| | >>: | | | c/| |>e | >>: | | C1 --- | | | >>: --- | 10uF--- |2N3906 | | >>: - V2 | | | | | >>: --- SINE(0 .2 1k) | | | | | C3 >>: - | C5 | | | | || 470uF >>: | | || 10p| | +----+-||----,O >>: | +V +---||----+ | | || |U >>: | | | || | | | |T >>: gnd | | | | | \ >>: | | | |2N3904 | / R5 >>: \ ,-------, | | | | \ 8 >>: / R3 | | | +V | Q1 c\| |<e Q5 / >>: \ 1k | +V | | | 2N| |-------| 2N3906 | >>: / | | | | |\| | e<| |\c | >>: | | |\| | '-|-\ | | | | >>: | '--|-\ | | >----+----' | gnd >>: | | >-+-----|+/ | >>: +-------|+/ |/| LT6234 | >>: ,-----+ |/| LT6234 | gnd >>: | | | gnd >>: --- C4 \ gnd >>: --- 1uF/ R9 >>: | \ 1k >>: | / >>: | | >>: gnd gnd > >(This was auto-generated from my LTspice to ASCII program.) > >Jon What in the world ?:-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
From: Jon Kirwan on 9 Feb 2010 17:50 On Tue, 09 Feb 2010 15:42:48 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote: >What in the world ?:-) View in fixed-spaced font. And it's a rendition of the schematic that Bob Monson had posted, earlier, from EDN. He wrote, "On a related note, there was an article in a recent EDN about a self biasing preamp which was kinda cool. Instead of trying to track the difference using diodes or a multiplier, it used a couple of transistors and an opamp to set the correct values at the bases of the pass transistors. It was so novel (at least to me) that I typed it into LTSpice." I merely re-arranged it in LTspice to be a little more to my taste and then passed it through a program that generates ASCII from that. Jon
From: Jon Kirwan on 9 Feb 2010 17:52 On Tue, 9 Feb 2010 23:38:06 +0100, "Ban" <bansuri(a)web.de> wrote: > >"Jon Kirwan" <jonk(a)infinitefactors.org> schrieb im Newsbeitrag >news:8te2n5llb72tgv03g653ajqjf360m3mc06(a)4ax.com... >> On Mon, 8 Feb 2010 18:23:16 -0800 (PST), "miso(a)sushi.com" >> <miso(a)sushi.com> wrote: >> >>><> >> Okay. I'll do that if folks here aren't interested at all in >> talking about it. >> >BS, a couple of good answers have come. Agreed. We are past that question. >Jon, you should read this book, bit torrentwise >Audio Power Amplifier Design Handbook, 4th Ed. - (Malestrom) >by Doug Self, one of the deeper going but still very practical publications, >you'll love it. >Ban I just received a copy of the 5th edition, today. I'll start, though the author says that it assumes a certain level of prior training. And skimming through, I agree. Jon
From: Jon Kirwan on 9 Feb 2010 18:01
On Tue, 09 Feb 2010 14:52:02 -0800, I wrote: >On Tue, 9 Feb 2010 23:38:06 +0100, "Ban" <bansuri(a)web.de> >wrote: > >> >>"Jon Kirwan" <jonk(a)infinitefactors.org> schrieb im Newsbeitrag >>news:8te2n5llb72tgv03g653ajqjf360m3mc06(a)4ax.com... >>> On Mon, 8 Feb 2010 18:23:16 -0800 (PST), "miso(a)sushi.com" >>> <miso(a)sushi.com> wrote: >>> >>>><> >>> Okay. I'll do that if folks here aren't interested at all in >>> talking about it. >>> >>BS, a couple of good answers have come. > >Agreed. We are past that question. > >>Jon, you should read this book, bit torrentwise >>Audio Power Amplifier Design Handbook, 4th Ed. - (Malestrom) >>by Doug Self, one of the deeper going but still very practical publications, >>you'll love it. >>Ban > >I just received a copy of the 5th edition, today. I'll >start, though the author says that it assumes a certain level >of prior training. And skimming through, I agree. Okay!!! It has a great section on Vbe multipliers under Chapter 15 on Thermal Compensation!! This is helpful. And it includes a discussion on that collector resistor there and in Chapter 7, where a chart is presented with various values for my R3 shown and the curves over current. Nice!! It also appears, on first glance, to confirm my impressions!! This is very good. Jon |