The response speed of the amplifier may be limited by the frequency band or by this slew rate. Generally, it is expressed by the amount of voltage change per micro second. This shows the maximum voltage rise rate of the amplifier. The second factor is a slew rate that represents the response speed of the amplifier. Generally, the rise time of the response speed (= frequency band) fc (Hz) amplifier can be obtained by tr ≑ 0.35/fc. The rise time and fall time are related to the frequency band. Therefore, it is necessary to select an amplifier with a frequency band with a margin for the frequency you want to use. The figure shows the frequency until the amplitude reaches -3 dB in the frequency band.įor example, when the frequency band of a 120 V rated amplifier is 20 kHz, even if it tries to output a ± 20 V sine wave at 20 kHz, the output amplitude becomes 70% at -3 dB, so it becomes a ± 14 V sine wave. At high frequencies, the amplifier cannot keep up with the input signal and the amplitude of signal decreases. The frequency band corresponds to the operating speed of the amplifier. In order to the electric current and voltage output values to stabilize, it is necessary to understand factors that inhibit them. From here, we will introduce what kind of things we should be careful about when designing and implementing amplifier. So far, we have explained the type and characteristics of the amplifier. Although MOSFETs and IGBTs are used as switching devices, there is also the problem that the frequency band of the corresponding input signal is narrow.Ĭonditions Necessary for Stable Operation of the Amplifier It is mainly used for compact audio power amplifiers such as automotive applications. This is more efficient and smaller than linear amplifiers by using switching technique such as PWM. Distortion is canceled by adding a bias current to a Class-B amplifier.Īnother amplifier is a "digital amplifier" also called switching amplifier, class-D amplifier. It is an amplifier that has a good reputation between Class-A and Class-B. Instead, there is no need for bias current like Class-A amplifiers, and the efficiency is improved. Therefore, when the input signal is near zero, the output signal is also zero and distortion occurs. This amplifier uses both the non-linearly and the linearly amplified region of the element as it is. That is, to ensure that the output signal is correct, it always keeps a constant bias current even when the input signal is zero. Therefore, although the linearity is high, it is necessary to supply a bias current (or voltage) even when the input signal is close to zero, which is disadvantageous in that the efficiency is degraded and the heat generation is large. This amplifier uses only the linearly amplified region of the element. We will introduce the four-quadrant bipolar power supply in detail at the last chapter. We call a two-quadrant bipolar power supply that can supply current sources of positive and negative charge, and a four-quadrant bipolar power supply that can supply also current sink. DC power supplies are also called unipolar (power supply) because of being able to supply positive charge only. In fact, the power supply is also a kind of amplifier. In addition, since the amplifier can supply any electric current and voltage (or electric power), it can also be used as a power supply simulator. It operates amplifying the electric signal output from the various sensor and making it easy to perform analog-to-digital conversion.Īn amplifier is a representative of analog circuits, and it is so central that there is nothing if the amplifiers are removed from the analog circuits. So, the amplifier is for amplifying the signal flowing in the electric circuit, and it amplifies the input current or voltage. Of course, in the electrical circuit, including audio power amplifier, the various signals are exchanged as electrical signals. The device that amplifies something is called an amplifier. But the "amplifier" itself is not just for audio.
If you search for "amplifier" on the Internet, you will get results for many web sites about audio power amplifier.
How to Use the Amplifier and Its Notes Type and Characteristics of Amplifier