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By analyzing of typical op-amp differentiator circuit considered the op-amp amplitude-frequency characteristic, we give out a design of sine-wave oscillator based on an improved op-amp differentiator. This oscillator is not only the output sine wave harmonic distortion very low, but also easy to design and easy to trimming to fine. Introduction At present the active RC sine-wave oscillator includes Wien’s bridge oscillator [1] and RC phase shift oscillator. The frequency selecting circuit of Wien’s bridge oscillator is two-order band-pass circuit, and its quality factor is 1/3. The frequency selecting circuit of RC advanced phase shift oscillator is three order high pass circuit. The frequency selecting circuit of RC delayed [2] phase shift oscillator is three-order low pass circuit. Their frequency characteristics are poor, so they output large harmonic component. This paper uses modified active RC differential circuit for frequency selecting circuit. By using the RC phase shift circuit, the phase condition of the oscillator is satisfied [3]. With variable gain amplifier, the amplitude condition and stability condition of the oscillator are also satisfied. The frequency of output sine-wave frequency of the circuit is close to the center frequency of the frequency selecting circuit. The quality factor of the frequency selecting circuit is usually greater than 10, so the output harmonic distortion of sine-wave is very low. The range of oscillation frequency is at least (0.0001~ 0.1) . is op-amp gain bandwidth product. The basic active RC differential circuit Figure 1 is the basic active RC differential circuit [4]. If the amplifier is the ideal op-amp, its transfer function is shown as below: ( ) H s sCR = − (1) Using EWB as simulation software, first-order op-amp model is type of LF353. With simulation of the circuit in Figure 1, we get the amplitude frequency characteristics of the transfer function, as shown in Figure 2. It is the same as the amplitude frequency characteristics of the two band pass filter. The transfer function of the basic active RC differential circuit is derived as follows with Figure 1 ( f0=99.79kHz,Q=39.4,Am=63dB) Figure 2 6th International Conference on Mechatronics, Materials, Biotechnology and Environment (ICMMBE 2016) © 2016. The authors Published by Atlantis Press 515 first-order op-amp model. 0 ( ) 1 p k A s T s = + (2) is the amplifier open-loop gain, 1/Tp is one pole. List current and loop voltage equations:

A Design of Sine-wave Oscillator Based on an Improved OP-amp Differentiator