英文原文
ducksMultivibrator
Abstract:
Frequently ud in digital systems, circuit multivibrator. Multivibrator is a lf-excited oscillator, after the power is turned on, the need for external trigger signal can be generated on a rectangular wave of a certain frequency and a certain width, this output waveform for the circuit of the clock signal source. The square wave rich in high harmonics, it ud to turn rectangular wave oscillator called a multivibrator. In accordance with the principle of the circuit, the multivibrator isbroadly divided into astable multivibrator and monostable multivibrator.
Key Words: Harmonic oscillator Trigger signal Duty-cycle Oscillation Period
1 Astable Multivibrator
1.1 TTL gate circuit compod of symmetrical astable multivibrator??Typical symmetrical multivibrator circuit shown in Figure 1, it is by two inverters Gl, G2 by the coupling capacitors C1, C2, connect the positive feedback oscillation circuit. Circuit G1 and G2 using SN74LS04N inverter RFl RF2 RF, C1 C
2 C and the oscillation period T ≈ 1.3RFC, the duty cycle of the output waveform is about 50%. RF1, RF2
resistance for LSTTL 470 Ω, ~ 3.9kΩ standard TTL between 0.5 ~ 1.9k Ω新年快乐英文歌曲
Figure 1 Symmetrical multivibrator type nsor
四年级下册英语辅导视频>condom1.2 The u of non-symmetrical astable multivibrator circuit of the CMOS gate??Further simplify the symmetrical multivibrator circuit, remove C1 and R2 in the feedback loop to keep the capacitor C2, the circuit is still not steady state, only in two temporary steady state reciprocating oscillation circuit shown in Figure 2 below.
Figure 2 Non symmetrical multivibrator type nsor
skyscraper1.3With 555 timer astable multivibrator??Schmitt trigger 555 circuits can be formed using the hysteresis characteristics of the Schmitt trigger, charge and discharge the capacitor C and the access between the two input and ground of the circuit feedback resistor between the output and input access Rf on the formation of a direct feedback multivibrator, as shown in Figure 3a Below. Power circuit after each flip charge-discharge process is the temporary steady state time and two temporary steady state, respectively capacitor charge time Tl and discharge time T宣布英语
2. T1 O. 69RfC, T2 0.69RfC, the oscillation period T T1 + T2, the oscillation frequency f 1 / T.
Figure3
Change the R and C valuescan change the charge and discharge time, ie to change the oscillation frequency f of the circuit Direct feedback
from the shortcomings of multi-harmonic oscillator is: due to charge the output capacitor C, as well as affected by load factors will cau the instability of the oscillation frequency. Indirect feedback to the multi-harmonic oscillator as shown in Figure 3b below, the circuit works the same, but its performance is greatly improved. Charging through R1 and R2 are two of the circuit resistance, the discharge resistor R2 a two temporary steady state time is not equal T1 0.69 R1 + R2 C, T2 0.69R2C oscillation period T T1 + T2 0.69 Rl +2 R2 C and oscillation frequency f 1 / T. If the circuit to improve the access diode D1 and D2, the circuit shown in Figure 4 c shows, the capacitor charge and discharge currents flowing through the different paths, the charging current only flows through R1, the discharge current only flows through R2, charge and discharge time of capacitor C, respectively, for T1 0.69R1C T2 0.69R2C, the oscillation period T T1 + T2 0.69 R1 + R2 C, the oscillation frequency f 1 / T. If we take R1 R2 50% duty cycle The 555 timer is a versatile digital-ana
log mixed integrated circuits, the u of flexible, convenient, and the 555 timer waveform generation and transformation, measurement and control, home appliances, electronic toys, and many other fields have been applied.
1.4 Quartz crystal multivibratorIn some circuits require a higher stability of the digital pul, the pul generated by veral multi-vibrator is difficult to meet the requirements. This is becau thenecessary
oscillation frequency of the oscillation circuit is incread by the gate input voltage to the conversion level needs time to decide. Affected by the supply voltage, temperature, and some confounding factors, the conversion time of the gate can not very preci and stable. The quartz crystal multivibrator that produces a pul of high stability oscillators, quartz crystal resonator in the feedback loop to the original multivibrator constitute The frequency stability of quartz crystal has a very high frequency stability up to 10-10 ~ 10-11, and the quality factor is high, so it has excellent frequency lection characteristics. When the applied voltage frequency is equal to the natural frequency of the quartz crystal f0, its minimum impedance, frequency f0 voltage signal is most easily pasd, Multivibrator oscillation frequency of the quartz crystal depends only on the quartz crystal's natural frequency f0, regardless of the external R, C components.
有声读物mp3Monostable multivibrator
2.1 Monostable multivibrator circuit??Using the TTL gate circuit monostable multivibrator circuit shown in Figure 4. Rl and R2 in the G1 input clamp, to improve the trigger nsitivity.
Figure 4
2.2 Integrated monostable multivibrator??Very common view of the monostable multivibrator, TTL circuits and 3CMOS circuit, the products are produced monolithically integrated monostable multivibrator devices. When using the devices only need a few external components and connections, and very convenient to u the device internal circuits are generally attached to the rising edge and falling edge trigger control and zero.汉英词典在线查询
2.2.1 Monostable ring oscillator circuit structure??The output pul of the monostable at all levels in order as a trigger to the trigger input signal, and then the final output signal is fed back to the first level, as the first level trigger input signal, can constitute a The new type of ring oscillator that is a single ring oscillatorMonostable delay effect, the the monostable ring oscillator waveform, as shown in The cycle of the oscillator output signal is: T T1 + T2 + L + Tn, where T1 i l, 2,., n for all levels of single-shot transient stability time?The same levels temporary stabilization time, the circuit is a typical quential pul generator, the waveform and the identical to the D flip-flop consisting of ring
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counter. Difference is that the ring counter must be performed by the same clock pul drive circuit output pul width and the cycle of the clock signal must be changed by changing the frequency of the clock signal to the output pul width. The monostable ring oscillator can be automatically generated pul signal, pul width can be adjusted by
