the signal path class c power amplifier tutorial

#The signal path class c power amplifier tutorial full
#The signal path class c power amplifier tutorial plus

There is also a small “dead zone”, a time during which neither switch is on, thus higher switching frequency makes the dead zone as short as possible so it does not affect the output signal. That means no in-band power supply noise, but also adds very high frequency noise at the output. The switching rate is usually well above the audio band, perhaps 100 kHz to 1 MHz. By eliminating standing current, a class D amplifier can achieve 90% or higher efficiency, meaning much lower average power and much less power wasted as heat. A class AB can achieve about 67% efficiency. A class AB amplifier reduces the current by only supplying current as needed to drive the load with minimal standing (constant) current just to cover the “gap” when the signal transitions from top and bottom devices.

#The signal path class c power amplifier tutorial full

A push-pull class A amp has full current flowing all the time and is at best 50% efficient. There is no standing bias current in the output devices as in a class A or class AB amplifier. That is the key to the high efficiency of a class D amplifier.

#The signal path class c power amplifier tutorial plus

Power is expended mainly as the signal is switched from high to low and back and the filter plus load (speaker) is charged when the switches are static, little power is needed, as the signal is supplied from the output filter. The switches connect the unfiltered output (Vamp) to either the positive (V+) or negative (V-) power supply rail. The controller can be complicated, but its basic job is to turn on either the high or the low switch, and never both at the same time! That would short the power rails through the switches, increasing power, heat, and chances of blowing up the amplifier. This is usually a logic circuit and voltage amplifier that drives the output switches. The comparator’s output (Vcmp) is applied to a controller. The other input to the comparator is a triangle wave more about that shortly. A comparator with a clocked latch after it is a basic building block for an analog-to-digital convert (ADC). Almost but not quite a true digital signal, which is quantized in time and amplitude. This converts the input from a purely analog signal to one that is quantized (sampled) in amplitude though not in time. The (-) input is the comparator’s threshold voltage.

In the real world perfection is hard to find, so the output will not be perfect even with feedback, but it can get pretty close as Amir’s measurements have shown.Īfter the buffer is a comparator, a circuit that outputs a “high” if the (+) input is above the (-) input and a “low” otherwise. lowering distortion) and stabilizing the circuit so part variations, power supply and temperature changes, and other effects do not reduce performance. The feedback signal allows the amplifier to correct any errors at the output, improving linearity (e.g. The output of the buffer is the difference between these two signals, providing a modified signal to the rest of the amplifier. The negative input of the opamp receives the feedback signal (Vfb) from the output (Vout). First the input signal, Vin, is applied to the input buffer (shown as an operational amplifier, opamp). It is a rather busy diagram, so we’ll step through each piece from input to output. The figure below is a simplified schematic diagram of a class D amplifier. Note the “D” does not mean “digital” it is simply the next letter in order as standards bodies enumerated amplifier types (A, B, C, D, E, F, G, H, I, etc.) It takes an analog, not digital, input and produces a pulse width modulated (PWM) output. This is a quick overview of how class D amplifiers operate.