Sample Application Circuit

For sample application circuit :

1.

The LB1412M consists of the following blocks.

.

Input amp 1: Amplification of input signal, variable with external constants

.

Input amp 2: Amplification of signal (fixed, double), detection of signal

.

Reference voltage : Reference voltage of comparator, constant-current drive of LED

.

Comparator : Comparison of input voltage

.

LED driver : LED drive, D1 to D7: Constant-current drive

.

Peak hold circuit : Hold of highest-order point of high-order 5 points (D8 to D12)

.

Oscillator for peak hold reset : Peak hold circuit reset

2.

Description of constants of each block

2-1 R3, R4 (R11, R12)

The gain of amp1 depends on R3, R4. Gain of amp 1 = R3/R4 times. The gain of amp1 must not exceed 4 times

(12 dB). R3 + R4

6 100 kΩ (C4 = 4.7 µF).

2-2 C2, C3 (C5, C6)

C3 is for coupling amp 1 with amp 2 and its value is 1 µF. C2 is for controlling the time to turn off LED.

2-3 R2 (R10)

The current of LEDs connected to D1 to D7 depends on R2. The current is stabilized to be approximately 17 mA at

R2=3k

Ω and approximately 11 mA at R2 = 4.7 kΩ.

2-4 R5 to R9 (R13 to R17)

The current of LEDs connected to D8 to D12 depends on these resistors. D8 to D12 pins are collectors of Darlington

transistors.

R5 to 9

6

R5 to 9

Unit (resistance:

Ω, capacitance: F)

Note : Input signal of approximately 110 mVrms causes D8 (0 dB display) to light.

R5 2.2 k

R6 2.2 k

R8 2.2 k

R7 2.2 k

R9 2.2 k

LB1412M

No.1593-4/5