4440 IC AMPLIFIER

     HOW TO MAKE A 4440 IC AMPLIFIER

LA4440 is a two channel audio power amplifier IC with inbuilt in dual channels enables it for stereo and bridge amplifier applications. In dual mode it gives 6 W per channel and in bridge mode 19 W output.

It has good ripple rejection of 46dB, small residual noise, built in over voltage and surge voltage protection etc. ideal feature of the IC is its pin-to-pin protection. Here LA4440 is wired in Stereo configuration using both inputs and outputs.

Features

• Built-in 2 channels (dual) enabling use in stereo and bridge

amplifier applications.

Dual : 6W´2 (typ.)

Bridge : 19W (typ.)

• Minimun number of external parts required.

• Small pop noise at the time of power supply ON/OFF and

good starting balance.

• Good ripple rejection : 46dB (typ.)

• Good channel separation.

• Small residual noise (Rg=0).

• Low distortion over a wide range from low frequencies to

high frequencies.

• Easy to design radiator fin.

• Built-in audio muting function.

• Built-in protectors.

a. Thermal protector

b. Overvoltage, surge voltage protector

c. Pin-to-pin short protector

Pin connection of LA4440
Pin
1 NF1
2 Audio In 1
3 Pre Amp Ground
4 Audio Mute
5 DC
6 Audio In 2
7 NF2
8 Gnd
9 BS 2
10 Audio Out 2
11 VCC
12 Audio Out 1
13 BS 1
14 Gnd

Equivalent Circuit Block Diagram

Sample Application Circuit 1. Stereo use

Sample Application Circuit 2. Bridge amplifier 1

Sample Application Circuit 3. Bridge amplifier 2

Description of External Parts

C1 (C2) · Feedback capacitor : The low cutoff frequency depends on this capacitor.

If the capacitance value is increased, the starting time is delayed.

C3 (C4) · Bootstrap capacitor : If the capacitance value is decreased, the output at low frequencies goes lower.

C5 (C6) · Oscillation preventing capacitor : Polyester film capacitor, being good in temperature characteristic,

frequency characteristic, is used.

The capacitance value can be reduced to 0.047mF depending on the stability of the board.

C7 (C8) · Output capacitor : The low cutoff frequency depends on this capacitor.

At the bridge amplifier mode, the output capacitor is generally connected.

C9 · Decoupling capacitor :Used for the ripple filter. Since the rejection effect is saturated at a certain

capacitance value, it is meaningless to increase the capacitance value more than required. This capacitor,

being also used for the time constant of the muting circuit, affects the starting time.

R1 (R2) · Filter resistor for preventing oscillation.

R3 (R4) · Resistor for making input signal of inverting amplifier in Voltage Gain Adjust at Bridge Amplifier

Mode (No. 1).

R5 · Resistor for adjusting starting time in Voltage Gain Adjust at Bridge Amplifier Mode (No. 2)

C10 · Capacitor for preventing oscillation in Voltage Gain Adjust at Bridge Amplifier Mode (No. 2)

C11 · Power source capacitor.

R6 (R7) · Used at bridge amplifier mode in order to increase discharge speed and to secure transient stability.

Feaures of IC System and Functions of Remaining Pins

(a) Since the input circuit uses PNP transistors and the input potential is designed to be 0 bias, no input coupling

capacitor is required and direct coupling is available. However, when slider contact noise caused by the variable

resistor presents a problem, connect an capacitor in series with the input.

(b) The open-loop voltage gain is lowered and the negative feedback amount is reduced for stabilization. An increase

in distortion resulted from the reduced negative feedback amount is avoided by use of the built-in unique distortion

reduction circuit, and thus distortion is kept at 0.1% (typ.).

(c) A capacitor for oscillation compensation is contained as a means of reducing the number of external parts. The

capacitance value is 35pF which determines high cutoff frequency fH (–3dB point) of the amplifier (fH»20kHz).

(d) For preventing the IC from being damaged by a surge applied on the power line, an overvoltage protector is

contained. Overvoltage setting is 25V. It is capable of withstanding up to 50V at giant pulse surge 200ms.

(e) No damege occurs even when power is applied at a state where pins 10, 11, and 12 are short-circuited with solder

bridge, etc.

(f) To minimize the variations in voltage gain, feedback resistor RNF is contained and voltage gain (51.5dB) is fixed.

Proper Cares in Using IC

· Maximum ratings

If the IC is used in the vicinity of the maximum ratings, even a slight variation in conditions may cause the maximum

ratings to be exceeded, thereby leading to breakdown. Allow an ample margin of variation for supply voltage, etc. and

use the IC in the range where the maximum ratings are not exceeded.

· Printed circuit board

When making the board, refer to the sample printed circuit pattern and be careful that no feedback loop is formed

between input and output.

· Oscillation preventing capacitor

Normally, a polyester film capacitor is used for 0.1mF + 4.7W. The capacitance value can be reduced to 0.047mF depending

on the stability of the board.

· Others

Connect the radiator fin of the package to GND.