[sdiy] Norton & OTA book

[harrybissell]

Ahhh... now the gloves come off :^P

The LM3900 is NOT an OTA or even close.

The LM3900 is similar to a Current Controlled Voltage Source.   It has VERY low
input impedance (almost a dead short to the negative supply)... and low output
impedance
like a normal opamp.  Think Current In, Voltge Out

OTA are more like Voltage Controlled Current Sources (actually they are the
product of diffential voltage and amplifier bias current... and the output is a
high impedace (current source).

The LM3900 'could' be a very useful block (more so than it is) if it had offered
quality...
as it is the specs are pretty poor.

There is an LM359 Dual Norton...  I asked Bob Pease if that one was any good but
he
didn't know

(Background - at one of the Nat Semi seminars I overheard Bob Pease dissin' the
LM3900
so I wanted to find out why... so I asked.  I always considered it a "piece of
poop" myself
but was thinking opamp, which it aint. Today I'd consider playing with the
LM359)

H^) harry

Tim Parkhurst wrote:

> Hi All,
>
> In searching for more info on the LM3900, I came across a book that looks
> interesting: "49 Easy Electronic Projects for Transconductance & Norton Op
> Amps" by Delton Horn.
>
> The table o' contents looks promising (Norton and OTA info, applications
> like VCOs and VCAs). It looks to be out of print, but Amazon shows half a
> dozen used copies with prices ranging from $5 to $20US. I've just ordered
> one, so I'll know in about a week if there's anything interesting in it. Has
> anyone else seen this book?
>
> Harry, if the LM3900 is a piece of poop ("LM3900 is NOT an opamp" and "has
> no precision"), are the other common OTAs a better choice?
>
> Tim (worn at the edges like a good used book) Servo
> "Imagination is more important than knowledge." - Albert Einstein
>
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