SL6270C GEC Plessey Semiconductors, SL6270C Datasheet - Page 3

• Manufacturer Part Number: SL6270C
• Description: Gain Controlled Microphone Preamplifier / Vogad
• Manufacturer: GEC Plessey Semiconductors

SL6270C
ELECTRICAL CHARACTERISTICS
Test conditions (unless otherwise stated):
Supply voltage Vcc: 6V
Input signal frequency: 1kHz
Ambient temperature: -30 C to +85 C
Test circuit shown in Fig. 4
APPLICATION NOTES
Voltage gain
differential but must be capacitor coupled. In the single-ended
mode the signal can be applied to either input, the remaining
input being decoupled to ground. Input signals of less than a
few hundred microvolts rms are amplified normally but as the
input level is increased the AGC begins to take effect and the
output is held almost constant at 90mV rms over an input
range of 50dB.
reducing the main amplifier voltage gain. The connection of a
lk resistor between pins 7 and 8 will reduce both by
approximately 20dB. Values less than 680 are not advised.
Frequency response
by the input, output and coupling capacitors. Normally the
coupling capacitor between pins 2 and 7 is chosen to give a
-3dB point at 300Hz, corresponding to 2.2, F, and the other
capacitors are chosen to give a response to 100Hz or less.
N.B.
Supply current
Input impedance
Differential impedance
Voltage gain
Output level
THD
Equivalent noise input voltage
The input to the SL6270 may be single ended or
The dynamic range and sensitivity can be reduced by
The low frequency response of the SL6270 is determined
1M
If input not AC coupled the resistance
between pins 4 and 5 must be less than 10 ohms.
Characteristics
Fig. 4 SL6270 test and application circuit
47µ
+6V
100n
INPUT
1
2
3
4
2.2µ
8
7
6
5
INPUT
Min.
40
55
22k
4.7n
10µ
(1k MIN LOAD)
Value
OUTPUT
Typ.
150
300
52
90
5
2
1
Max.
140
10
of a few MHz and a capacitor should be connected between
pins 7 and 8 to give the required bandwidth.
Attack and delay times
holding the output level almost constant as the input is
increased. This ‘attack time’, the time taken for the output to
return to within 10% of the original level following a 20dB
increase in input level, will be approximately 20ms with the
circuit of Fig.4. It is determined by the value of the capacitor
connected between pin 1 and ground and can be calculated
approximately from the formula:
the capacitor and the recommended circuit gives a decay rate
of 20dB/second. Other values of resistance between pin 1 and
ground can be used to obtain different results.
5
The SL6270 has an open loop upper frequency response
Normally the SL6270 is required to respond quickly by
Voltage gain =
Upper frequency response 10k /4.7nk = 3kHz
Lower frequency response 680 /2.2 F = 300Hz
The decay time is determined by the discharge rate of
mV rms
Units
mA
dB
%
V
680
Fig. 5 SL6270 frequency response
Attack time = 0.4ms/ F
Pin 4 or 5
72 V rms input pin 4
4MV rms input pin 4
90mV rms input pin 4
300
2
EXTERNAL
2.2µ
10k
680
7
source, 400Hz to 25kHz bandwidth
EXTERNAL
4.7n
10k
Conditions
8