High-Frequency Semiconductors Power Devices
High-Frequency Semiconductors Power Devices
High-Frequency Semiconductors Power Devices
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
[ 5 ] Device Features in Detail<br />
3. <strong>High</strong>t-Freguency 3-Pin MOSFET<br />
This 3-pin MOSFET is a new device that leads current electronics technology.<br />
Prior to introduction of this further innovation, the dual-gate MOSFET has been the most popular<br />
type of conventional high-frequency MOSFET.<br />
In this device, Gate 2 already had features offering several advantages when compared to<br />
junction-type FETs or bipolar transistors.<br />
Generally, Gate 2 can be used as the local oscillation signal injector terminal for mixer circuits, and<br />
an AGC terminal.<br />
However, there is an alternative application technique for dual-gate MOSFETs, as shown in<br />
Figure 3.1. This shows a typical high-frequency amplifier in a Hi-Fi tuner. In the circuit depicted by<br />
this figure, Gate 2 is used only as a DC fixed-bias terminal, in order to achieve power gain.<br />
Dual-gate MOSFET<br />
MIX<br />
ANT<br />
Unnecessary<br />
2 resistors and<br />
1 condenser 3-terminal MOSFET<br />
can be saved.<br />
V DD<br />
Dual-gate MOSFET<br />
G 1<br />
S G 2<br />
D<br />
ANT<br />
MIX<br />
G<br />
3-terminal MOS FET<br />
D<br />
S<br />
V DD<br />
Figure 3.1 Figure 3.2<br />
Assuming that a dual-gate MOSFET can achieve good performance when the Gate 2 bias voltage is<br />
zero, Gate 2 only needs to be grounded; however, in practice, in this device Gate 2 has to be biased in<br />
a voltage range of 3 to 5 V.<br />
Passive components required for this purpose are at least two resistors and one capacitor.<br />
However, a 3-terminal MOSFET does not require such components, yet can achieve the same<br />
characteristics as a dual-gate MOSFET.<br />
The 3-terminal MOSFET is a cascode-connected device, in which Gate 2 of the dual-gate MOSFET<br />
is connected to the source.<br />
In addition, special consideration has been given to maintaining excellent performance even when<br />
Gate 2 is zero biased: this is achieved by using the channel control from the Gate 2 side.<br />
Moreover, our original manufacturing technique allows reliability is improved by a decrease in the<br />
amount of bonding.<br />
Three types of packages are available, suitable for current compact FM tuners: Mini Mold (2SK241),<br />
Super Mini (2SK302), and Ultra Super Mini (2SK882).<br />
57
Change language