EUA2011

DS2011 Ver 1.1 Dec. 2007

14

Summing Two Single-Ended Input Signals

Four resistors and three capacitors are needed for

summing single-ended input signals. The gain and corner

frequencies (fc1 and fc2) for each input source can be set

independently (see equations (9) through (12), and Figure

35). Resistor, RP, and capacitor, CP, are needed on the

IN+ terminal to match the impedance on the IN− terminal.

The single-ended inputs must be driven by low impedance

sources even if one of the inputs is not outputting an ac

----------------------(9)

---------------------(10)

-----------------------------------------(11)

----------------------------------------

-(12)

-------------------------------------------(13)

------------------------------------- (14)

Figure 35. Application Schematic with EUA2011

Summing Two Single-Ended Input

PCB Layout

As output power increases, interconnect resistance (PCB

traces and wires) between the amplifier, load and power

supply create a voltage drop. The voltage loss on the

traces between the EUA2011 and the load results is lower

output power and decreased efficiency. Higher trace

resistance between the supply and the EUA2011 has the

same effect as a poorly regulated supply, increase ripple

on the supply line also reducing the peak output power.

The effects of residual trace resistance increases as output

current increases due to higher output power, decreased

load impedance or both. To maintain the highest output

voltage swing and corresponding peak output power, the

PCB traces that connect the output pins to the load and the

supply pins to the power supply should be as wide as

possible to minimize trace resistance.

The use of power and ground planes will give the best

THD+N performance. While reducing trace resistance, the

use of power planes also creates parasite capacitors that

help to filter the power supply line.

The inductive nature of the transducer load can also result

in overshoot on one or both edges, clamped by the

EMI stand- point, this is an aggressive waveform that can

radiate or conduct to other components in the system and

cause interference. It is essential to keep the power and

output traces short and well shielded if possible. Use of

ground planes, beads, and micro-strip layout techniques

are all useful in preventing unwanted interference.

As the distance from the EUA2011 and the speaker

increase, the amount of EMI radiation will increase since

the output wires or traces acting as antenna become more

efficient with length. What is acceptable EMI is highly

application specific.

Ferrite chip inductors placed close to the EUA2011 may

be needed to reduce EMI radiation. The value of the

ferrite chip is very application specific.

1

I

R

k

150

2

1

I

V

O

V

1

Gain

Ω

×

=

=













V

V

2

I

R

k

150

2

2

I

V

O

V

2

Gain

Ω

×

=

=













V

V

()

1

c

1

I f

R

2

1

1

I

C

π

=

()

2

c

2

I f

R

2

1

2

I

C

π

=

2

I

1

I

C

C

CP

+

=

()

2

I

R

1

I

R

2

I

R

1

I

R

P

R

+

×

=