BA1404 and upc1651 produced by the modulator circuit

BA1404 is Toyo's products, operating voltage range of 1 ~ 3V, the circuit is from the FM stereo mixer, 38KHZ oscillator, FM modulator and high-frequency amplifier monolithic integrated circuit.

Works (see Figure I): stereo audio signal and by increasing the input matching network consists of 1,2 feet, the amplified FM stereo into the mixer, to produce a main signal from the L + R and LR stereo sub-signal composite signal composed of amplified by the buffer from 14 feet out (16,17 feet to adjust the parameters of the composite signal, can control the left and right balance); 4,5,6 pin external discrete components and internal oscillator circuit 38KHZ 38KHZ signal by the buffer supply of mixers and amplification, respectively, 1 / 2 divider, 38KHZ 19KHZ signal by the divider to get a pilot signal from 13 feet out; 13-14 feet out from the composite signal and the pilot signal by the matching network consists of 11 feet into the FM Modulator (9,10 feet of production sub-component to determine the external oscillation frequency) to produce a FM signal, the amplified output from 7 feet; 2 feet for the AF offset 3 feet for the AF ground point, 8 feet is the RF connection location, 15 feet for the positive power supply. (Note: a reference voltage output pin 11 to facilitate external discrete components to control the oscillation frequency, where not used.) 7 foot by μpc1651 final amplified output signal.

Production Highlights: circuit board can be used in the million-intensive to install, to remove the excess copper point; 13,14 feet, only the reference value of resistance, because of its value on the stereo separation are related, according to the actual situation given value; L for the iron shell variable inductance, its parameters and frequency-related, here is the critical frequency stabilization, be careful; If you want electricity supply, pay attention to power, the current small, discrete filter can be regulated power; μpc1651 the working voltage is 5V, not exceed, easy to burn.

Experiment Summary: As the "electronic newspaper" BBS there are many users requiring detailed information on the FM stereo transmitter, so I re-collect the relevant information on the simple discrete, merge, integrated FM stereo transmitter experiment, that The BA1404 + μpc1651 mix of the most easy to make and debug, and very high frequency stability (relative to the previous circuit BA1404), transmission power does not exceed the statutory range.

参数	单位	测试条件	最小值	典型值	最大值
静态电流	IQ(mA)		3.5	3	5
输入电阻	Rin(KΩ)	f=1KHZ	360	540	720
输入增益	GV(dB)	Vin=0.5mv	30	37
声道平衡	CB(dB)				2
混合器输出最大电压	Vom(mvp-p)	THD=<3%	200
38KHZ泄漏电压	Voo(mv)	无信号时		1
导频输出电压	Vop(mvp-p)	无负载时	460	580
声道分离度	Sep(dB)		25	45
输入噪声	Vin(μV)			1
高放输出最大电压	Vosc(mV)		350	600