Saturday, July 13, 2013
LA4440 Bridge Amplifier Circuit Diagram
LA4440 is a dual channel audio amplifier IC. It can be used in two modes; one is Stereo amplifier and another Bridge amplifier mode. The LA4440 is a monolithic linear IC from Sanyo. Here I give the both circuit mode of amplifier using IC LA4440.
When the IC LA4440 is in Bridge mode in the circuit, its output power is 19w. In bridge mode use 4Ω-8Ω speaker. If you want stereo output(19w+19w) in bridge mode then use two copies of amplifier circuit of given below. Resistor R3&R4 is to adjust the voltage gain and for making input signal of inverting amplifier.
C10 is filter capacitor used to reduce the ripple of supply voltage. Don’t decrease the value of capacitor C6&C7 less than 100uF, 10v, it may causes of the output at low frequencies goes lower. The pin-6 of LA4440 amplifier circuit is audio input pin; it used in stereo amplifier mode but in bridge mode it is grounded. C8&C9 are polyester film capacitor used to preventing oscillation, and R1&R2 used for the same reason as filter resistor. Though the maximum supply voltage for both circuit of amplifier is 18V but we recommend to use a 12V,3A power supply. Use a good quality heat sink with LA4440.
Wednesday, April 3, 2013
Using TLV2471 for Wein Bridge Oscillator
The Wien - Bridge oscillator is one of the simplest and best known oscillators and is used extensively in circuits for audio applications. The figure in the below shows the basic Wien bridge circuit configuration. On the positive side, this circuit has only a few components and good frequency stability. The major drawback of the circuit is that the output amplitude is at the rails, which saturates the op-amp output transistors and causes high output distortion.
The gain, A, of the negative feedback portion of the circuit must then be set. RF must be set to twice the value of RG to satisfy this condition. The op amp in the figure is single supply, so a dc reference voltage, VREF, must be applied to bias the output for full-scale swing and minimal distortion. Applying VREF to the positive input through R2 restricts dc current flow to the negative feedback leg of the circuit. VREF was set at 0.833V to bias the output at the mid rail of the single supply, rail-to-rail input and output amplifier, or 2.5 V, (see reference in the data sheet of oscillator). VREF is shorted to ground for split supply applications.
The Wien – Bridge oscillator circuit is shown in the figure, with component values selected to provide an oscillation frequency of 0 = 2f0, where f0 = 1/(2RC) = 1.59 kHz. The circuit oscillated at 1.57 kHz, caused by varying component values with 2.8% distortion. This high value results from the extensive clipping of the output signal at both supply rails, producing several large odd and even harmonics. The feedback resistor was then adjusted 1%. Figure 9 shows the output voltage waveforms. The distortion grew as the saturation increased with increasing RF, and oscillations ceased when RF was decreased by a mere 0.8%.