Monday, April 19, 2010

LM3876 - High-Performance 56W Audio Power Amplifier with Mute


The LM3876 is a high-performance audio power amplifier capable of delivering 56W of continuous average power to an 8 load with 0.1% THD+N from 20Hz-20kHz.The performance of the LM3876, utilizing its Self Peak Instantaneous Temperature protection circuitry, puts it in a class above discrete and hybrid amplifiers by providing an inherently, dynamically protected Safe Operating Area. Speaker protection means that these parts are completely safeguarded at the output against overvoltage, undervoltage, overloads, including shorts to the supplies, thermal runaway, and instantaneous temperature peaks.The LM3876 maintains an excellent signal-to-noise ratio of greater than 95dB (min) with a typical low noise floor of 2.0µV. It exhibits extremely low THD+N values of 0.06% at the rated output into the rated load over the audio spectrum, and provides excellent linearity with an typical rating of 0.004%.

Features

56W continuous average output power into 8Ω

100W instantaneous peak output power capability

Signal-to-Noise Ratio >= 95 dB(min)

An input mute function

Output protection from a short to ground or to the supplies via internal current limiting circuitry

Output over-voltage protection against transients from inductive loads

Supply under-voltage protection, not allowing internal biasing to occur when VEE + VCC <= 12V, thus eliminating turn-on and turn-off transients

11-lead TO-220 package

Wide supply range 20V - 94V

Part list

Resistor:
R1, R3 = 1 k
R2, R4, R5 = 18k
R6 = see text
R7 = 10R, 5 Watt
R8, R9 = 22k

Capacitors:
C1 = 2.2 uF
C2 = 220 uF, 160 V
C3 = 22 uF, 40 V
C4 = 47 pF
C5 = 100 uF, 40 V
C6 = see text
C7, C8 = 100 nF
C9, C10 = 1000 uF, 40 V
Inductors:
L1 = 0.7 uH – see text

Integrated circuits:
IC1 = LM3876T

Miscellaneous:
Heat sink for IC1

Air-cored inductor L1 consists of 13 turns of 1mm dia. enamelled copper wire with an inner diameter of 10mm. The completed inductor is pushed over R7 and its terminals soldered to those of the resistor. All electrolytic capacitors must be mounted upright. The amplifier can be muted with a single-pole switch connected to the MUTE input (pin8). This function is enabled when the switch is open. If muting is not required, solder a wire bridge across the mute terminals on the board. The R6-C6 is not normally required in this application, but provision has been made for it for use in other applications. According to the manufacturers, both chips are optimalized for a load of 8 Ohm. The output power is lower when a 4 Ohm load is used or when the supply voltage is reduced. When a 4 Ohm load is used, the SPIKE protection becomes active when the supply voltage is about 27V, resulting a in a reduction of the power output to 10W. This means that it is not advisable to use loudspeaker with an impedance

[read here...]

Sunday, April 18, 2010

LM1875 - POWER AMPLIFIER 20 WATT


The LM1875 is a monolithic power amplifier offering very low distortion and high quality performance for consumer audio applications.
The LM1875 delivers 20 watts into a 4Ω or 8Ω load on ±25V supplies. Using an 8 load and ±30V supplies, over 30 watts of power may be delivered. The amplifier is designed to operate with a minimum of external components. Device overload protection consists of both internal current limit and thermal shutdown.
The LM1875 design takes advantage of advanced circuit techniques and processing to achieve extremely low distortion levels even at high output power levels. Other outstanding features include high gain, fast slew rate and a wide power bandwidth, large output voltage swing, high current capability, and a very wide supply range. The amplifier is internally compensated and stable for gains of 10 or greater.

Features

• Up to 30 watts output power
• AVO typically 90 dB
• Low distortion: 0.015%, 1 kHz, 20 W
• Wide power bandwidth: 70 kHz
• Protection for AC and DC short circuits to ground
• Thermal protection with parole circuit
• High current capability: 4A
• Wide supply range 16V-60V
• Internal output protection diodes
• 94 dB ripple rejection
• Plastic power package TO-220
[read here...]