Frekans Cevabı(Tepkisi) / Frequency Response

The Frequency Response of an amplifier or filter shows how the gain of output reacts to input signals at different frequencies.Amplifiers and filters are commonly used electronic circuits with upgrade and filtering capabilities. While amplifiers produce gain, filters change amplitude and/or phase properties according to the frequency of an electrical signal. Since these amplifiers and filters use resistors, inductors or capacitor networks (RLC) in their design, there is an important relationship between the use of these reactive components and the frequency response characteristics of circuits. When dealing with AC circuits, it is assumed that they work at a constant frequency, for example, at 50 Hz or 60 Hz. But the response of a linear AC circuit can also be examined by an AC or sinusoidal input signal of a fixed size but varying frequency, such as those found in the amplifier and filter circuits. This then allows such circuits to be studied using frequency response analysis. Frequency Response of an electrical or electronic circuit allows us to see exactly how the output gain (known as the magnitude response) and phase (known as phase response) change at a specific single frequency or at all different frequencies. From 0Hz, (dc) to thousands of mega-hertz, (MHz), depending on the design characteristics of the circuit. In general, frequency response analysis of a circuit or system is shown by plotring its gain, i.e. the output signal, against the input signal, against a frequency scale that the Output/Input is expected to run on the circuit or system. Then knowing the gain (or loss) of circuits at each frequency point helps us to understand how well (or bad) the circuit can distinguish signals at different frequencies. The frequency response of a circuit connected to a specific frequency can be displayed as a graphical drawing of the magnitude (gain) against the frequency (ε). While the horizontal frequency axis is usually drawn on a logarithmic scale, the vertical axis representing voltage output or gain is usually drawn as a linear scale in decimal chambers. Because a system gain can be both positive and negative, the y-axis can therefore have both positive and negative values. In electronics, Logarithm, or "log" for short, is defined as the power that must be raised to obtain this number. Then, in a Bode chart, the logarithmic x-axis scale is rated with log10 sections, so that every ten years the frequency (for example, 0.01, 0.1, 1, 10, 100, 1000, etc.) is placed evenly on the x-axis. The opposite of logarithm is an anthrharism or "anthologist". Graphical representations of frequency response curves are called Bode Charts, and therefore Bode drawings are often said to be semi-logarithmic charts because one scale (x-axis) is logarithmic and the other (y-axis) is linear.

Frequency Response Curve

frequency response Next, we can see that the frequency response of any circuit is a change in its behavior with changes in input signal frequency, as it indicates the frequency band, which remains quite constant above the output (and gain). The frequency range large or small between εL and εH is called circuit bandwidth. Thus, we can determine the voltage gain (in dB) at a glance for any sinusoidal input in a certain frequency range. As mentioned above, the Bode diagram is a logarithmic representation of frequency response. Most modern sound amplifiers have a flat frequency response, as shown above, in the entire range of sound frequencies from 20 Hz to 20 kHz. For an audio amplifier, this frequency range is called Bandwidth (BW) and is primarily determined by the frequency response of the circuit. Frequency points εL and εH relate to the lower corner or cutting frequency and upper corner or cutting frequency points respectively, indicating that circuit gain decreases at high and low frequencies. These points on a frequency response curve are commonly known as -3dB (decibel) points. Therefore, bandwidth is simply given as frequency response follows: Decibels (dB), which are 1/10 of the waist (B), are a common nonlinear unit for measuring gain and are defined as 20log10(A), where A is the decimal gain drawn on the y-axis. . Zero decibels (0dB) correspond to a size function of the unit that outputs the maximum output. In other words, since there is no weakening at this frequency level, 0dB occurs when Vout = Vin is formed and given as follows: frequency response

From the Bode chart above, we see that the output at two corners or cutting frequency points has decreased from 0dB to -3dB and continues to fall at a constant rate. This decrease or decrease in earnings is commonly known as the rolling region of the frequency response curve. In all basic single-row amplifier and filter circuits, this roll-off speed is defined as 20dB/ten years, equivalent to a 6dB/octave speed. These values are multiplied by the order of the circuit.

These -3dB corner frequency points define the frequency at which the output gain is reduced to 70.71% of the maximum value. Then we can accurately say that the point -3dB is also the frequency at which the maximum value of the systems' earnings drops to 0.707.

Frequency Response at -3dB

frequency response The -3dB point is also known as half power points, since the output power at these corner frequencies will be half the maximum 0dB as shown. frequency response Therefore, the amount of output power transmitted to the load is effectively "halved" at the cutting frequency, and therefore the bandwidth (BW) of the frequency response curve can also be defined as the frequency range between these two half power points. . We use 20log10 (Av) for voltage gain and 20log10 (Ai) for current gain and 10log10 (Ap) for power gain. Keep in mind that the multiplication factor with 20 does not mean that the decibel is twice as high as 10, since it is a unit of the power ratio and there is no measure of the actual power level. In addition, gain in dB can be positive or negative, indicating a positive gain and a negative value weakening. Then we can present the relationship between voltage, current and power gain in the table below.

Decibel Gain Equivalents

dB GainVoltage or Current Gain 20log10(A)Power Gain 10log10(A)
-30.7071 or 1/√20.5
31,414 or √22
601,0001 million

OPAMPs can have open loop voltage gains (AVO) exceeding 1,000,000 or 100dB.

Decibel Example

If an electronic system produces an output voltage of 24mV when a 12mV signal is applied, calculate the decibel value of the system output voltage.

frequency response

Decibel Example

If the output power of an audio amplifier is measured at 10W when the signal frequency is 1kHz and 1W when the signal frequency is 10kHz. Calculate the dB change in power. frequency response


In this context, we saw how the frequency range on which an electronic circuit works is determined by the frequency response. The frequency response of a device or circuit defines how its gain or amount of signal allowed changes with the frequency, allowing it to operate in a specific range of signal frequencies. Bode graphics are graphical representations of the frequency response properties of circuits and can therefore be used to solve design problems. Usually the circuits gain size and phase functions are shown in separate graphs using the logarithmic frequency scale along the x-axis. Bandwidth is the frequency range at which a circuit operates between the upper and lower cutting frequency points. These cutting or corner frequency points indicate frequencies where the power associated with the output drops to half the maximum value. These half-power points correspond to a 3dB (0.7071) earnings drop based on the maximum dB value. Most amplifiers and filters feature a flat frequency response in which the bandwidth or transition band portion of the circuit is flat and constant in a wide frequency range. Resonance circuits are designed to bypass a number of frequencies and block others. They are constructed using resistors, inductors and capacitors, whose colorances vary according to frequency.