Relaxation oscillators are widely used in applications with relaxed phase-noise requirements in a form of fully integrated circuits as they do not consists of inductors. In contrast to LC oscillators, relaxation oscillator consist only one energy storing element.
振荡波形取决于电路的非线性特性，而不是频率选择性元件。因此，这些易于制造为整体式集成电路。
大纲
放松振荡器
Relaxation oscillators are non-sinusoidal oscillators which generate triangular, square and pulse waveforms using a circuit building block known as multivibrators. When the loop gain is greater than unity and the feedback is positive then the output produced is nearly similar to the sine wave which last for most of the periodic time.
在该状态下，放大器要么处于饱和状态，要么切断。这些类型的振荡器称为松弛振荡器。
In such oscillators, amplifiers used act as high-gain amplifier for short period of time and then wait for a change to takes place. Therefore, the frequency of oscillations does not directly depend on natural frequency of LC circuit or phase shift.
放大器不在电路的活动部分的时间间隔决定振荡的频率。松弛振荡器使用设备更改状态和RC正时电路来生成周期性输出波形。
在振荡的一个阶段，松弛振荡器将能量存储在反应性元件或组件中，并在周期的下一阶段中逐渐释放能量。
The relaxation oscillator concept is illustrated in the above figure in which a flash bulb is illuminated periodically for certain interval of time. The circuit arrangement consists of a battery, capacitor and bulb with 5V firing threshold.
When the capacitor is charged to the firing threshold level of the blubs, the capacitor starts discharging and supplies its stored energy to the blub.Then the bulb starts flashing for a time given by the time constant of the capacitor and resistor combination.
闪光灯后，电容器再次开始充电，这将是继续或重复的。重复时间取决于充电时间。相同的原理在松弛振荡器中应用，因此是重复的电路。
Relaxation oscillators are divided into two classes namely sawtooth oscillators and astable multivibrators. In first case, conduction of switching device causes the capacitor to discharge rapidly and instantly so the total output waveform takes up by the charging period alone virtually.
在明显的类型中，电容器的充电和放电都会通过电阻缓慢地进行。因此，总输出波形由这两个时期贡献。
UJT松弛振荡器电路
下图说明了使用Unijunction晶体管（UJT）的弛豫振荡器的构建。在UJT的发射极端子上连接的RC组合电路决定了振荡的频率。电阻R1和R2用作电流限制电阻，如图所示。
When the circuit is energized with DC voltage, UJT remains in OFF condition and the capacitor starts charging through the resistance R. Since the emitter terminal of the UJT is connected to the capacitor, the capacitor voltage considerably effects the performance of UJT. When the voltage across the capacitor becomes the peak voltage of the UJT, UJT is driven into conduction mode.
在此阶段，发射器– Base1抗性崩溃，因此电容器开始排放。当电容器上的电压变成UJT的山谷点电压时，Amiiter-Base1电阻会恢复到高电阻，因此UJT驱动到截止模式。
因此，电容器再次开始充电，并重复此过程，并在电容器上产生锯齿波形，如图所示。
可观的多振动器电路
它是一种松弛振荡器，会产生周期性的方波。方波的幅度在一段时间内是恒定的，之后它突然变为另一个级别，进一步保持恒定，这些突然的变化定期进行。
The below figure shows the astable multivinrator circuit in which continuously generates square wave without any external signal. It consists of two stage resistance coupled amplifiers and output of the each stage is coupled to each other as regeneration as shown in figure.
It consists of two quasi stable states and the associated circuit changes its state from one quasi state to the other without any triggering.
当给电路提供电源时，T1的导致T2超过T2（由于两个阶段电路的不对称组件会失效），这意味着T1的收集器电流大于T2的收集器电流，因此VC1小于VC2。
由于该电压VC1耦合到T2的基部，因此T2的收集器电流进一步降低，最后VC2接近VCC。该过程将继续进行，直到晶体管T1完全打开并且T2完全关闭。这是C2通过RC2充电的一个准稳定状态。
Meanwhile the capacitor C1 (which was already charged) discharges through T1 and R1making base of the T2 suddenly Vcc. Therefore, no current flows through the base of T1 and it stops conducting. Now, T2 starts conducting as the base current to it increases.
该过程将继续进行，直到T2完全打开并且T1完全关闭。这是另一个准稳定状态。电压VC1和VC2采用平方波形，在整个过程继续进行时，它们相互互补。
放松振荡器Circuit using Opamp
The figure below shows an operational amplifier version of relaxation oscillator in which the output switches back and forth between the two saturation limits of the op-amp. The output is taken at the operational amplifier output and this output charges the capacitor through the resistor R.
When the power supply is given to the circuit, the capacitor starts charging towards Vcc through the resistor R. Whenever the voltage across the capacitor reaches to the trigger voltage of the op-amp, the op-amp switches and the output voltage reverses to its opposite saturation limit.
然后，通过电阻器的电流会改变符号，电容器开始放松相反的阈值。运算放大器的正输入处的扳机阈值电压也发生了变化，因此当电容器电压达到该阈值时，Op-Amp输出再次改变其状态。
This process will be repeated. Typical waveforms of the op-amp output voltage and voltage across the capacitor are shown in figure.
使用555计时器的放松振荡器电路
放松振荡器或astable multivibratorcan be implemented by using555计时器and its circuit is given below. The pulse width of the output waveform depends on the RC time constant. The circuit is connected as, Pin 4 is connected directly to the supply; Pin 6 and Pin 2 are shorted together; and at Pin 3 output is taken out.
When the supply voltage is given to the circuit, the capacitor starts charging using the power supply Vcc. Then the output is high at pin 3 (due to the open discharge terminal).
当电容器电压达到2/3 VCC时，内部触发器的变化会变化，并且放电端子短短到地面，因此输出量低。可以通过改变电阻和电容器的值来改变工作频率。
通过以这种方式操作555个计时器，它没有稳定的状态，这仅意味着它不能无限期地保持在任何一个州。因此，在输出末端获得了一系列矩形脉冲。
放松振荡器的应用
这些振荡器用于许多应用中，其中一些示波器在下面列出。
- 示波器
- 电视接收器
- 频镜
- Electronic camera flashes
- 在数字电路中生成时钟信号
- 用于发射基于晶闸管的电路和设备
