![]() ![]() ![]() In other words, the capacitor C behaves as if its capacitance is (1 + beta)*C. With this circuit, the capacitance C is amplified to (1 + beta)*C, where beta is the gain provided by the transistor. If the input voltage is sufficiently high, you can set the output voltage by adjusting the values of R1 and R2. If you are driving the capacitance multiplier at a lower input voltage, then you need to apply a lower collector-base voltage (i.e., R2 > R1) to ensure the transistor enters saturation. Simple capacitor multiplier with a transistorĭriving the transistor to saturation is important here as this suppresses ripple on the input voltage from changing the output voltage. However, this increases the collector-emitter voltage drop, which increases power dissipation as heat. By using R2 in parallel with the capacitor, the transistor is more easily driven into saturation as the collector-base voltage is lower, thus the output from the transistor will saturate at a lower level. Simple capacitance multiplier circuits sometimes omit R2 to provide higher output voltage, but this reduces the level of noise suppression provided by this circuit. In this circuit, the two resistors function as a voltage divider that regulates the voltage applied to the base of the transistor and the voltage drop across the transistor. This circuit is inherently nonlinear and takes advantage of saturation in a transistor.Ī simple capacitance multiplier circuit with a transistor is shown in the figure below. Note that a capacitance multiplier, whether or not it uses a transistor, is not a voltage regulator, although it can certainly be used in conjunction with a standard linear regulator (on the input or output) or a switching regulator (normally on the input). A transistor with higher DC gain (beta value) provides a larger capacitance multiplication factor in a capacitance multiplier circuit, thus BJTs are not normally used in capacitance multipliers as their gain is ~1. The first way to build a capacitance multiplier circuit is to use an FET (or MOSFET). This circuit causes a capacitor to behave like a much larger capacitor, which provide much better smoothing in power supply circuits. In terms of design and layout, you can easily design a capacitance multiplier from discrete components or an operational amplifier IC. A capacitance multiplier is a deceptively simple circuit for power conditioning and removing ripple on the output from a power supply. There are some interesting linear circuits that can be used to decrease the noise floor in a circuit by removing noise from a power supply’s output.Īn excellent circuit that can remove residual ripple voltage and other noise sources is a capacitance multiplier. ![]() Filtration and amplifier circuits are always fun to play with. I always like to get down to the gritty details of different circuits, and I enjoy building them myself on a breadboard. All these components are important parts of your power conditioning strategy ![]()
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