EL2227CS 데이터 시트보기 (PDF) - Elantec -> Intersil

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EL2227CS

Dual very low noise amplifier

Elantec -> Intersil 

EL2227C

Dual Very Low Noise Amplifier

Disable Function

The EL2227C is in the standard dual amplifier package

without the enable/disable function. A simple way to

implement the enable/disable function is depicted

below. When disabled, both the positive and negative

supply voltages are disconnected (see Figure 2 below.)

+12V

1k

10k

10k

1k

+

-

1µF

1µF

4.7µF

1k

75k

Power Dissipation

With the wide power supply range and large output drive

capability of the EL2227C, it is possible to exceed the

150°C maximum junction temperatures under certain

load and power-supply conditions. It is therefore impor-

tant to calculate the maximum junction temperature

(TJMAX) for all applications to determine if power sup-

ply voltages, load conditions, or package type need to be

modified for the EL2227C to remain in the safe operat-

ing area. These parameters are related as follows:

TJMAX = TMAX + (θJA × PDMAXTOTAL)

where:

PDMAXTOTAL is the sum of the maximum power dissi-

pation of each amplifier in the package (PDMAX)

PDMAX for each amplifier can be calculated as follows:

PDMAX

=

2 × VS × ISMAX + (VS

–

VOUTMAX

)

×

V-----O----U----T----M-----A----X--

RL

where:

TMAX =Maximum Ambient Temperature

θJA =Thermal Resistance of the Package

PDMAX =Maximum Power Dissipation of 1 Amplifier

VS =Supply Voltage

IMAX =Maximum Supply Current of 1 Amplifier

VOUTMAX=Maximum Output Voltage Swing of the

Application

RL =Load Resistance

To serve as a guide for the user, we can calculate maxi-

mum allowable supply voltages for the example of the

video cable-driver below since we know that TJMAX =

150°C, TMAX = 75°C, ISMAX = 9.5mA, and the package

θJAs are shown in Table 1. If we assume (for this exam-

ple) that we are driving a back-terminated video cable,

then the maximum average value (over duty-cycle) of

VOUTMAX is 1.4V, and RL = 150Ω, giving the results

seen in Table 1.

Table 1

Part

EL2227CS

EL2227CY

Package

SO8

MSOP8

θJA

160°C/W

206°C/W

Max PDISS @

TMAX

0.406W @ 85°C

0.315W @ 85°C

Max VS

Single-Supply Operation

The EL2227C have been designed to have a wide input

and output voltage range. This design also makes the

EL2227C an excellent choice for single-supply opera-

tion. Using a single positive supply, the lower input

voltage range is within 200mV of ground (RL = 500Ω),

and the lower output voltage range is within 875mV of

ground. Upper input voltage range reaches 3.6V, and

output voltage range reaches 3.8V with a 5V supply and

RL = 500Ω. This results in a 2.625V output swing on a

single 5V supply. This wide output voltage range also

allows single-supply operation with a supply voltage as

high as 28V.

Gain-Bandwidth Product and the -3dB

Bandwidth

The EL2227C have a gain-bandwidth product of

137MHz while using only 5mA of supply current per

amplifier. For gains greater than 2, their closed-loop ----

-3dB bandwidth is approximately equal to the gain-

13

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