![]() ![]() ![]() Again, other properties of the ideal buffer are: perfect linearity, regardless of signal amplitudes and instant output response, regardless of the speed of the input signal.įor a current buffer, if the current is transferred unchanged (the current gain β i is 1), the amplifier is again a unity gain buffer this time known as a current follower because the output current follows or tracks the input current.Īs an example, consider a Norton source (current I A, parallel resistance R A) driving a resistor load R L. In the ideal current buffer in the diagram, the output impedance is infinite (an ideal current source) and the input impedance is zero (a short circuit). The interposed buffer amplifier prevents the second circuit from loading the first circuit's current unacceptably and interfering with its desired operation. Typically a current buffer amplifier is used to transfer a current from a first circuit, having a low output impedance level, to a second circuit with a high input impedance level. A Thévenin equivalent circuit of the combined original Thévenin source and the buffer is an ideal voltage source V A with zero Thévenin resistance. At the output the dependent voltage source delivers voltage A v V A = V A to the load, again without voltage division because the output resistance of the buffer is zero. However, if the Thévenin source drives a unity gain buffer such as that in Figure 1 (top, with unity gain), the voltage input to the amplifier is V A, and with no voltage division because the amplifier input resistance is infinite. Because of voltage division (also referred to as "loading") the voltage across the load is only V A R L / ( R L + R A ). However, it is commonplace to say that it has a gain of 1 (or the equivalent 0 dB), referring to the voltage gain.Īs an example, consider a Thévenin source (voltage V A, series resistance R A) driving a resistor load R L. ![]() Although the voltage gain of a voltage buffer amplifier may be (approximately) unity, it usually provides considerable current gain and thus power gain. If the voltage is transferred unchanged (the voltage gain A v is 1), the amplifier is a unity gain buffer also known as a voltage follower because the output voltage follows or tracks the input voltage. Other properties of the ideal buffer are: perfect linearity, regardless of signal amplitudes and instant output response, regardless of the speed of the input signal. In the ideal voltage buffer in the diagram, the input resistance is infinite and the output resistance zero (output impedance of an ideal voltage source is zero). The interposed buffer amplifier prevents the second circuit from loading the first circuit unacceptably and interfering with its desired operation, since without the voltage buffer the voltage of the second circuit is influenced by output impedance of the first circuit (as it is larger than the input impedance of the second circuit). Two main types of buffer exist: the voltage buffer and the current buffer.įigure 1: Top: Ideal voltage buffer Bottom: Ideal current buffer Voltage buffer Ī voltage buffer amplifier is used to transfer a voltage from a first circuit, having a high output impedance level, to a second circuit with a low input impedance level. The signal is 'buffered from' load currents. Electronic amplifier, a circuit componentĪ buffer amplifier (sometimes simply called a buffer) is one that provides electrical impedance transformation from one circuit to another, with the aim of preventing the signal source from being affected by whatever currents (or voltages, for a current buffer) that the load may impose. ![]()
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