LM1875 AUDIO AMPLIFIER 20W

LM1875 general description:

LM1875 pcb layout

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 8Ω 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.

LM1875 amplifier circuit:

LM1875 AUDIO AMPLIFIER 20W

LM1875 power supply diagram:

LM1875 power supply diagram

LM1875 pcb layout:

LM1875 pcb layout

LM1875 project review:

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TDA8922 Audio Amplifier 2x25W

TDA8922 general description:

The TDA8922 is a high efficiency class-D audio power amplifier with very low dissipation. The typical output power is 2 × 25 W. The device is available in the HSOP24 power package with a small internal heatsink and in the DBS23P through-hole power package. Depending on the supply voltage and load conditions, a very small or even no external heatsink is required. The amplifier operates over a wide supply voltage range from ±12.5 to ±30 V and consumes a very low quiescent current.

TDA8922 features:

• High efficiency (∼90%)
• Operating supply voltage from ±12.5 to ±30 V
• Very low quiescent current
• Low distortion
• Usable as a stereo Single-Ended (SE) amplifier or as amono amplifier in Bridge-Tied Load (BTL)
• Fixed gain of 30 dB in Single-Ended (SE) and 36 dB in
• Bridge-Tied Load (BTL)
• High output power
• Good ripple rejection
• Internal switching frequency can be overruled by an external clock
• No switch-on or switch-off plop noise
• Short-circuit proof across load and to supply lines
• Electrostatic discharge protection
• Thermally protected.

TDA8922 applications:

• Television sets
• Home-sound sets
• Multimedia systems
• All mains fed audio systems
• Car audio (boosters).

TDA8922 amplifier diagram, circuit:

TDA8922 pcb layout:

TDA7490 Audio Amplifier 2x25W

TDA7490 general description:

The TDA7490 is a dual audio class D amplifier assembled in Flexiwatt 25 package; it is specially designed for high efficiency application mainly for TV and Home Stereo sets.

TDA7490 features: 

• 25W + 25W OUTPUT POWER:
• RL = 8Ω/4Ω; THD = 10%
• HIGH EFFICIENCY
• WIDE SUPPLY VOLTAGE RANGE (FROM
• ±10 TO ±25V)
• SPLIT SUPPLY
• TURN OFF/ON POP FREE
• ST-BY AND MUTE FEATURES
• SHORT CIRCUIT PROTECTION ACROSS
• THE LOAD
• THERMAL OVERLOAD PROTECTION
• EXTERNALLY SINCHRONIZABLE
• BRIDGE CONFIGURATION

TDA7490 amplifier diagram, circuits:

TDA7490 Audio Amplifier 2x25W

TDA7490 layout, pcb:

TDA7490 layout, pcb

TDA7490 layout, pcb

TDA1562Q Audio Amplifier 50W

 TDA1562Q general description:

Philips designers have further improved a number of properties of the IC, among which the power output. According to the Philips datasheet, the improved device, the TDA1562Q, can deliver 70 watts into 4 ohms, but that is at the cost of the distortion, which at 10 per cent is rather too high, even for in a car. The prototype of the design described in this article provides 54 watts into 4 ohms at 1 per cent distortion. Since the number of requisite external components is smaller than in the case of the earlier device, the printed-circuit board is even more compact than that for the February 1995 amplifier.

 TDA1562Q features:

• Low power dissipation during reproduction of music signals
• Proof against short-circuits
• Protection against excessive temperatures
• Standby switch
• No power-on or power-off clicks
• Visible error indication
• Measurement results (at Ub=14.4 V)
• Supply voltage 8–18 V
• Sensitivity 760 mV r.m.s.
• Input impedance 70 kΩ
• Power output 54 W r.m.s. into 4 Ω (f=1 kHz; THD+N=1%)
• Harmonic distortion (THD+) at 1 W into 4 Ω: 0.046% (1 kHz)0.29% 20Hz) at 35 W into 4 Ω: 0.12% (1 kHz) 0.7% (20 kHz)
• Signal-to-noise ratio (with 1 W into 4 Ω) 88 dBA
• Power bandwidth 7.5 Hz – 185 kHz (at 25 W into 4 Ω)
• Quiescent current about 135 mA (‘on’)

TDA1562Q applications:

• Television sets
• Home-sound sets
• Multimedia systems
• All mains fed audio systems
• Car audio (boosters).

TDA1562Q amplifer diagram:

TDA1562Q pcb:

TDA1562Q part lists:

• R1= 1MΩ
• R2 = 4kΩ7
• R3 = 1kΩ
• R4 = 100kΩ
• Capacitors:
• C1,C2 = 470nF
• C3,C4 = 10µF 63V radial
• C5,C6,C8 = 4700µF 25V radial
• (18mm max. dia., raster 7.5 mm)
• C7 = 100nF, raster 5 mm
• Semiconductors:
• D1 = high-efficiency-LED
• IC1 = TDA1562Q (Philips)
• Miscellaneous:
• S1 = single-pole on/off switch
• Four spade connectors, PCB mount
• Heatsink for IC1 (Rth<2.5 K/W)
• PCB, order code 000004-1 (see Readers Services pages)

100w audio amplifier

General description:

 

All resistors are standard metal film 250mW except: R1/3/4/7, these are 2W metal film, and the 0.22ohm beeing 5W. Around R7 is wounded a 0.6mm isolated (enamelled) copper wire forming the output coil. (~12 windings)  For c19 i used 470uf/16v, all other electrolytics 63v. The 10/100/330pF should be mica-caps. The 100nf and 47nf is recommended to be Wima MKS2 (or better), also for C1 i suggest Wima MKS2, 4.7uf is enough. For Trimpot i use a Piher. The MPSA18 can be substituted by BC550C, for all other parts i do not recommend changes, especially the feedback network (r29/30) should be kept unchanged, feedback compensation is very delicate for this circuit ! Be careful when substituting the MPSA18 with BC550C, the pinout is reversed between these 2 transistors !!! The bias is adjusted via the trimpot (R22). Recommended bias is 55ma, resulting in 12mv across a single 0.22ohms or 24mv across both 0.22ohms. Connect a DMM to the upper wires of these resistors and adjust trimpot until DMM reads wanted voltage.

Features:

 

THD: ~0.005% (measured) sim'd: 0.002%
Power into 8ohm: 60 watts
Power into 4ohm: 100 watts
Gain: 32dB (~1:40) full output at 0.7v input (0.5v rms)
Feedback: 57dB
GainBandWidth: ~400Mhz
Slewrate: ~20v/us (symetrical)
Supply voltage: +/- 36v
Biasing: 55ma, ~12mv across a single 0.22 ohm
Measurings:The measuring setup itself is far from perfect, but gives a good idea !
Frequency response: 3.2hz to 145khz (-1db) using 4.7uf input cap
Phaseshift at 10khz: <3°
More will follow !

Circuit Diagram:

100w audio amplifier  circuit diagram

 

Layout Diagram:

100w audio amplifier  layout diagram

Partlist:

Device	Qty	Value	Notes
Q1,Q2	2	MPSA18	can be substituted by BC550C (pins reversed !)
Q7,Q8	2	BC546B	or maybe 2n5551 (pins reversed !)
Q3,Q9	2	2N5551	OnSemi/Fairchild/Philips
Q4,Q5,Q12	3	2N5401	OnSemi/Fairchild/Philips
T1	1	BD139	or bd135, bd135-16
U$5	1	MJE15030	OnSemi
U$6	1	MJE15031	OnSemi
U$3	1	MJL3281A	OnSemi
U$4	1	MJL1302A	OnSemi

Device	Qty	Value	Notes
C14	1	10pF (has been 22pF)	Mica
C2,C7	2	100pF	Mica
C3,C4	2	330pF	Mica
C18	1	47nF	Wima MKS2
C5, C6, C10, C11, C16, C17, C20	7	100nF	Wima MKS2
C1	1	10uF (4.7uF also fits)	Wima MKS2
C8,C9	2	100uF	Electrolytic 63v (at least 40v)
C19	1	470uF	Electrolytic 16v
C12,C13	2	1000uF	Electrolytic 63v (at least 40v)

Device	Qty	Value	Notes
R27,R28	2	0R22	5Watts
R1, R3	2	1R2	2Watts metal film
R4	1	4R7	2Watts metal film
R7	1	10	2Watts metal film
R2	1	10	250mW metal film
R8, R9	2	22	250mW metal film
R31, R32	2	47 (have been 22)	250mW metal film
R26	1	33	250mW metal film
R10	1	68	250mW metal film
R15,R17	2	150	250mW metal film
R11	1	220	250mW metal film
R24,R30	2	499 (or 500)	250mW metal film
R5,R6	2	680	250mW metal film
R13,R23	2	2k	250mW metal film
R12,R14,R29	3	22k	250mW metal film
R18,R20	2	47k	250mW metal film
R22	1	1k pot	Piher, small (470ohm might be better)

Device	Qty	Value	Notes
F1,F2	2	2.5T Fuse	Slow blow
F1,F2	2	---	Fuse holder
L1	1	---	0.6mm isolated (enamelled) copper wire wounded around R7 forming the output coil.