Op-amp circuit

Wien bridge oscillator with FET

Wien bridge oscillator is sine wave oscillator. It can generate a big of frequencies. The oscillator has based on a bridge circuit, which compose four resistors and two capacitors.

The oscillator can also be viewed as a positive gain amplifier combined with a band pass filter that provides positive feedback.

The field effect transistor (FET) Q1 works in the linear resistive region to give automatic gain control.
For the reduction of the RC network is one-third at the zero phase-shift tremble frequency,

The amplifier gain determined by resistor R1 and equivalent resistor RT must be just equal to three to make up the unity gain positive feedback requirement needed for stable oscillation.
Resistors R2 and R3 are set to approximately 1000 ohm less than the required R1 resistance.
The FET – 2N5020 dynamically provides the trimming resistance needed to make RT one-half of the resistance of R1.
The circuit composed of R4, D1, and C1 isolates, rectifies, and filters the output sine wave, converting it into a dc potential to control the gate of the FET.
For the low drain-to-source voltage used, the FET provides a symmetrical linear resistance for a given gate to source voltage.

Be the first to comment - What do you think? Posted by admin - February 27, 2012 at 9:32 am

Categories: Op-amp circuit, Oscillator generator Tags: bridge oscillator circuit, fet oscillator circuit, wien bridge oscillator circuit

High pass active filter by LM741

The high pass filter circuit is a high frequency filter, only through it. In this circuit we are use operational amplifiers IC 741 number, it is allows this circuit has a lot performance,and has cut off frequency precise. Despite the possibility of multi-circuit filter,With different levels of growth and differentiation of a roll back in the op-amp IC. But this circuit can reduce the frequency cut off, so successful, the device configuration, R1 = R2, C1 = C2.

Be the first to comment - What do you think? Posted by admin - September 26, 2011 at 11:10 pm

Categories: Op-amp circuit, Oscillator generator Tags: active high pass filter circuit, lm741 circuits

Simple function generator using LM1458

As usual the function generator will be expensive and difficult.However, this is a simple circuit with only two ICs.
This circuit is suitable for experiments. The output is 3 waveform , Square wave signal amplitude 7Vp-p, Triangular wave = 2Vp-vp and sine wave = 2Vp-p all have the frequency 1kHz.
We use 2 x LM1458 IC number, is the main equipment this a dual op-amp IC. This circuit uses op-amp 4 section, follow circuit image.
The IC1a is square wave generator, Assumed initial, C1 is charging voltage at inverting input pin to zero, Until voltage at non inverting input voltage is slightly positive.(A ratio of the op-amp output offset voltage determined by R1 and R2)
This time difference of the voltage input Enough to make the output of an op-amp in the volatility as a “high”.
When the output becomes high, C1 begins charging, the voltage at pin inverting, start over non-inverting input, an output swing to push down to zero.
which C1 Discharging again.
This is different from the first round, the amplifier output to an inverse alternating between low and high indefinitely. This produces a rectangular signal.
In the middle of the second op-amp. Defined as is integrator system, the input of the op-amp second is a square wave signal. The object of the first op-amp,.
The output of the op-amp is a triangle wave, whose amplitude is 2Vp-p only.
The triangular signal through op-amp 3, which determines the signal integrator, The output its image as a sine,.
Through to the fourth op-amp to amplify the signal to increase, with the inverting amplifier, the signal phase with the third op-amp.
This circuit use power supply: +9 V and-9V, IC number RC4558, or LF353 ICs used instead.