SN75374

QUADRUPLE MOSFET DRIVER

SLRS028 – SEPTEMBER 1988

3–10

POST OFFICE BOX 655303

APPLICATION INFORMATION

driving power MOSFETs

The drive requirements of power MOSFETs are much lower than comparable bipolar power transistors. The

input impedance of a FET consists of a reverse biased PN junction that can be described as a large capacitance

in parallel with a very high resistance. For this reason, the commonly used open-collector driver with a pullup

resistor is not satisfactory for high-speed applications. In Figure 13(a), an IRF151 power MOSFET switching

an inductive load is driven by an open-collector transistor driver with a 470-

Ω pullup resistor. The input

product of input capacitance and the pullup resistor is shown in Figure 13(b).

0

0.5

1

1.5

2

2.5

3

0

1

2

3

4

t – Time –

µs

470

Ω

1/2

SN75447

M

IRF151

48 V

TLC555

48

7

6

21

5

3

5 V

(a)

(b)

Figure 14. Power MOSFET Drive Using SN75447

A faster, more efficient drive circuit uses an active pull-up as well as an active pull-down output configuration,

referred to as a totem-pole output. The SN75374 driver provides the high-speed totem-pole drive desired in an

application of this type, see Figure 14(a). The resulting faster switching speeds are shown in Figure 14(b).

IRF151

0

0.5

1

1.5

2

2.5

3

0

1

2

3

4

t – Time –

µs

1/4

SN75374

M

48 V

TLC555

48

7

6

21

5

3

5 V

(a)

(b)

Figure 15. Power MOSFET Drive Using SN75374