Variable-Tone Signal Generating Circuit

Published:2011/4/22 21:40:00 Author:Sue | Keyword: Variable-Tone, Signal, Generating | From:SeekIC

Variable-tone signal generating circuit can be used in making different types of alarms, and can also in toys which will bring about a lot of fun. As seen in the figure, this circuit comprises relaxation oscillatory composed of unijunction transistor VT1, multivibrator composed of VT2, VT3, and B-type push pull power amplifier composed of VT4, VT5. The selection of component is as follows. VT1: Double-base diode BT33C, the direct current resistance RBB of which between b1 and b2 should be 3~10kΩ. VT2,VT3: 9013，50≤β≤85. VT4,VT5: 3DGl28，50≤β≤65. (In order to guarantee the accuracy of frequency, the parameters of geminate transistors VT2 and VT3, VT4 and VT5 should be as consistent as possible.) Power switch S1: KNX(1×1). Selected switch S2: KZX-1-3W1D(band switch). Audio transformer T: can-type ferrite MTT22, high-intensity enamelled wire L1-2ΦO．13mm, coiled by 380 turns; high-intensity enamelled wire L2-3ΦO.13mm, coiled by 380 turns; high-intensity enamelled wire L4-5Φ0.19mm, coiled by 46 turns. Resistance R12: 1/2 WRJ-type Other resistances: 1/8WRJ-type.



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