Can this SN7400 be replaced with 4011? What tube do you use? Coil parameters? 7400 is TTL (bipolar circuit), 4011 is CMOS (field-effect circuit) is generally not suitable for replacement, these gate circuits are now In both are very cheap. The output of the integrated circuit should be a pulse signal to stimulate the output transistor. Due to the role of the LC circuit on the collector of TR1, the final output sine wave frequency is mainly determined by the LC resonant circuit. Because TR1 is actually a switching tube, almost any high-frequency transistor can be selected when the excitation is sufficient. Since the 7400 is a pulse excitation signal that outputs a certain frequency, it should be possible to replace it with another circuit to output the same or different excitation signals. Besides, it is not convenient to use two different voltages. The above SN7400 is connected as an "inverter" to form an oscillation circuit. In principle, similar ICs can be used for testing. The frequency of the oscillator is determined by the crystal (XTAL) in the feedback loop; the "resonant frequency" of the LC resonant circuit of the output loop should be the same as XTAL, otherwise it will lose the meaning of the crystal "steady frequency"! -Of course, as an experiment, it is not necessary to use crystals. According to the parameters of the oscillator flag and the presence of a CX (transistor base) capacitor, it is estimated that the oscillation frequency of the oscillator is approximately in the order of MHz. You can consider using 4011 (general CMOS) or 74HC04 or 74HC14 (high speed CMOS) inverter IC for testing. However, a reminder: high-power output transmitters are limited (radio control)! Since the final stage is a bipolar transistor, the β value of the high-power transistor is relatively small, so it is better to promote him or the TTL circuit (transistor-transistor integrated circuit). To be larger than an order of magnitude. If the last stage is changed to small and medium power tube, you may also experiment with CM0S or PMOS circuit. The front-end circuit is a common gate circuit oscillator, which is found in various digital circuit books. Beijing Electronic News in 1994 seems to have a collection of oscillators. The most important thing is the TR1 tube, which is the core of the circuit, and it will be wasted without it! |
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