CLC5802IM datasheet(10/12 Pages) NSC

10 / 12 page

Application Information (Continued)

A resistive divider made from the 143

Ω and 60.4Ω resistors

was chosen to reduce the loop-gain and stabilize the net-

work. The CLC5802 composite integrator provides integra-

tion over five decades of operation. R and C set the integra-

tor’s gain.

Figure 4 shows the frequency and phase

response of the circuit in

Figure 3 with R = 44.2

Ω and C =

360pF.

K: R2/(R1 + R2)

0: Op amp low Frequency open loop gain

Positive Peak Detector

The CLC5802’s dual amplifiers can be used to implement a

unity-gain peak detector circuit as shown in

Figure 5.

The acquisition speed of this circuit is limited by the dynamic

resistance of the diode when charging C

hold. A plot of the cir-

cuit’s performance is shown in

Figure 6 with a 1MHz sinusoi-

dal input.

A current source, built around Q1, provides the necessary

bias current for the second amplifier and prevents saturation

when power is applied. The resistor, R, closes the loop while

diode D

2 prevents negative saturation when VIN is less than

C. A MOS-type switch (not shown) can be used to reset the

capacitor’s voltage.

The maximum speed of detection is limited by the delay of

the op amp and the diodes. The use of Schottky diodes will

provide faster response.

Adjustable or Bandpass Equalizer

A “boost” equalizer can be made with the CLC5802 by sum-

ming a bandpass response with the input signal, as shown in

Figure 7.

The overall transfer function is shown in

Equation (3).

(3)

To build a boost circuit, use the design Equation 4 and 5.

(4)

(5)

Select R

2 and C using Equation (4). Use reasonable values

for high frequency circuits - R

2 between 10Ω and 5kΩ, C be-

tween 10pF and 2000pF. Use

Equation (5) to determine the

parallel combination of R

a and Rb. Select Ra and Rb by ei-

ther the 10

Ω to 5kΩ criteria or by other requirements based

on the impedance V

IN is capable of driving. Finish the design

by determining the value of K from

Equation (6).

DS101341-29

FIGURE 4.

DS101341-30

FIGURE 5.

DS101341-31

FIGURE 6.

DS101341-32

FIGURE 7.

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