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Issue A

LANSDALE Semiconductor, Inc.

ML1350

GENERAL OPERATING INFORMATION

The input amplifiers (Q1 and Q2) operate at constant emitter

currents so that input impedance remains independent of AGC

action. Input signals may be applied single–ended or differen-

tially (for AC) with identical results. Terminals 4 and 6 may be

driven from a transformer, but a DC path from either terminal

to ground is not permitted.

AGC action occurs as a result of an increasing voltage on the

base of Q4 and Q5 causing these transistors to conduct more

heavily thereby shunting signal current from the interstage

amplifiers Q3 and Q6. The output amplifiers are supplied from

an active current source to maintain constant quiescent bias

thereby holding output admittance nearly constant. Collector

voltage for the output amplifier must be supplied through a

center–tapped tuning coil to Pins 1 and 8. The 12 V supply

(V+) at Pin 2 may be used for this purpose, but output admit-

tance remains more nearly constant if a separate 15 V supply

(V+ +) is used, because the base voltage on the output amplifi-

er varies with AGC bias.

AGC Amplifier Section

Input Amplifier Section

Bias Supplies

Output Amplifier Section

AGC

Input 70

2

(+)

V + +

8

1.47k

12.1

k

5.53k

470

Q6

Q5

Q3 Q4

470

5

2.0k

Output

1 ( – )

Q7

Q10

Q8 45 Q9

2.8k

200

200

2.8k

200

1.4k

1.9k

5.6k

8.4k

7

Gnd

1.1k

5.0k

Q1

Q2

66

4 ( – )

Inputs

6 ( + )

5.0k

1.1k

Figure 4. Circuit Schematic

V+

Figure 6. Power Gain, AGC and Noise Figure Test Circuits

(b) Alternate 45 MHz

*Connect to ground for maximum power gain test.

All power supply chokes (Lp), are self–resonant at input frequency. LP ≥ 20 kΩ.

See Figure 5 for Frequency Response Curve.

ML1350

4

3

2

1

5

6

7

8

RS = 50Ω

C1

5.1k

VAGC

0.68µH .001

0.1

0.001

Input

+12V

RL = 50Ω

Output

0.33µH

L1

C2

C3

5.1k

0.001

(a) 45 MHz and 58 MHz

+12V

0.001µF

Input

RS = 50Ω

C2

LP

LP

LP

1.5–20pF

4

3

2

1

T1

Output

RL = 50Ω

5

6

7

8

5.1k

VAGC *

ML1350

0.001µF

0.001

µF

C1

L1

0.001µF

0.001µF

0.001µF

T1 Primary Winding

Secondary Winding

Slug

= 18 Turns on a 1/4" coil form, center–tapped, #25 AWG

= 2 Turns centered over Primary Winding @ 45 MHz

= 1 Turn @ 58 MHz

= Carbonyl E or J

L1 @ 45 MHz = 7 1/4 Turns on a 1/4" coil form

L1

Ferrite Core

14 Turns 28 S.W.G.

C1

C2

C3

5–25 pF

5–25 pF

5–25 pF

45 MHz

58 MHz

L1

0.4 µH

Q ≥ 100

0.3 µH

Q ≥ 100

T1

1.3 µH to 3.4 µH

Q ≥ 100 @ 2.0 µH

1.2 µH to 3.8 µH

Q ≥ 100 @ 2.0 µH

C1

50 pF to 160 pF

8.0 pF to 60 pF

C2

8.0 pF to 60 pF

3.0 pF to 35 pF

Figure 5. Frequency Response Curve

(45 MHz and 58 MHz)

Scale: 1.0 MHz/cm