SN75374

QUADRUPLE MOSFET DRIVER

SLRS028A − SEPTEMBER 1988 − REVISED NOVEMBER 2004

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 an 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 14a, 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 14b.

0

1

2

3

4

IRF151

0

0.5

1

1.5

2

2.5

3

t − Time −

µs

470

Ω

1/2

SN75447

M

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 pullup, as well as an active pulldown 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 15a). The resulting faster switching speeds are shown in Figure 15b.

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

5 V

(a)

(b)

3

Figure 15. Power MOSFET Drive Using SN75374