Ton Giesberts
About the article

FM Stereo Decoder

For our Mini FM Receiver

FM Stereo Decoder
In February 2009 we published a monaural mini FM receiver. A matching stereo decoder will naturally make this receiver complete. In this mini project we deploy a TDA 7040 IC for this purpose. This IC has been available for quite a few years already and has by now amply proven its capabilities.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Component list

(all SMD shape 0805)
R1 = 47kO
R2,R4 = 4kO7
R3 = 270kO
R5 = 120kO
R6,R7,R9 = 33O
R8,R10 = 22kO
P1 = 50kO preset, SMD, e.g. Vishay Sfernice TS53YJ503MR10 (Farnell # 1557940)
P2 = 100kO preset, SMD, e.g. Vishay Sfernice TS53YJ104MR10 (Farnell # 1557934)
P3 = 6-way pinheader and stereo 22kO (25kO) logarithmic potentiometer

C1 = 270pF, SMD 0805 case
C2,C5,C7,C9 = 220nF, SMD 0805 case
C3,C4 = 100nF, SMD 0805 case
C6,C8 = 10nF, SMD 0805 case
C10 = 220µF 16V, radial, lead pitch 2.5 mm, diameter 6.5 mm max.
C11,C12 = 100µF 25V, radial, lead pitch 2.5 mm, diameter 6.5 mm max.

IC1 = TDA7040T, SMD SO8 case
IC2 = TDA7050T, SMD SO8 case

K1,K3 = 2-way pinheader
S1 (K2) = 1 make contact with 2-way pinheader
K4 = 3-way pinheader
BT1 = 2-way pinheader and 3-6 V battery (pack) and battery holder
PCB ref. 080907-1, available from

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