G8MNY TECH 24.08.19 06:12l 63 Lines 3160 Bytes #365 (0) @ WW
BID : 18748_GB7CIP
Subj: LM380N/TDA2003 IC Audio Amps
Path: OK0NBR IR2UBX DB0RES DB0OVN DB0GOS ON0AR GB7CIP
Sent: 190824/0906Z @:GB7CIP.#32.GBR.EURO #:18748 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW

From: VE2ACT@VE2TOY.#MTL.QC.CAN.NOA (Updated Mar 06)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
AUDIO PREAMP. avec IC LM 380N

10uF ┌──o ──o─────────────────────────────o+ o───||───┐ │ 200 ┌────────┐ 9V.
▓ ┌──────────────────┴────────────┐ uF │▓▓▓▓▓▓▓▓│ o-
Mic. 25k ▓ ────┤2 14 8├───||───┤▓▓▓▓▓▓▓▓│ │
input ▓ │ IC LM 380N │ + │speaker │ │
│ │6 │ └────┬───┘ │ o────────┤ │ 1 3 4 5 7 9 10 11 12 │ │ │
│ └──┬──┬──┬──┬──┬──┬───┬───┬───┬─┘ │ │
│ │ └──┴──┴──┴─┬┴───┴───┴───┘ │ │
│ .01 === │ │ │
└────────┴─────────────┴────────────────────────────┴─────────┘

======================================================================
de VE2ACT..........MONTREAL en packet.....janv04..(D55 audioamp.asc) ------------------------------------------------------------------------------- G8MNY Comments: Idealy a large C across the supply to help stability & reduce battery supply dips on peak 1/2 cycles. For hify use the 200uF LS C should be 1000uF if 4 or 8Ω bass loudspeaker useds. ------------------------------------------------------------------------------- Here is one using a TDA2003
By G8MNY

Sensitivity
40mV 60KΩ ┌────────┬────┬───────────── +8-18V 0.5A ┌─────┐
o────┐ │ u1 === === 1000uF │ 0 │
Vol┌┴┐ + 1│\│5 _│_ _│_ 25V ├─────┤
Pot│ │ ──┤├────┤+ \ 4 │ │
100k│ │ 10uF │ ─────┬───┬────┤├─────┬──o LS └┬┬┬┬┬┘
Log└┬┘ ┌─────┤- / ┌┴┐ ┌┴┐ + 1000uF │ 7W Music/ │2│4│
│ │ 2│/│3 100Ω│ │ │ │ 16V ┌┴┐ 3.5W RMS into 1 3 5
│ │+ │ └┬┘ └┬┘470Ω │ │1Ω 4Ω LS @ 18V
│ ├─┤├────)────────(───┤ └┬┘ 0.05% dist
│ │470uF │ 8n2 │ ┌┴┐ │ 20Hz-20KHz (-3dB)
│ └───────)───┤├───┘ │ │4.7Ω === 86dB S/N
│ │ └┬┘ 0.1uF ├──o LS o────┴────────────┴────────────┴───────────┴── -

HOW IT WORKS
The input Z of the IC is 150k so with the 100k pot this is approx 60k depending on the slider position. The IC power rail is well decoupled at LF with the 1000uF & @ HF with the u1 cap.

The gain setting NFB is in 2 parts, the basic gain of 100x by the 470Ω/4.7Ω, & the HF cut to 20x by 100Ω/4.7Ω & 8n2 for stability. Also for stability is the "Zobal network" of a 1Ω in series with u1 across the LS, this keeps the output stage terminated at HF.

This design with its high IC open loop gain with loads of NFB gives very low distortion, but poor HF stability & possably poor transiant intermod distortion (TIMD)!


Why Don't U send an interesting bul?

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