In this paper high voltage NPN bipolar junction transistors (BJT) in 4H-SiC are presented for applications in low frequency switching as well as in UHF (425 MHz) power amplifiers. The power 2 BJTs were designed to block 1400 V and showed a specific on-resistance of 5.3 mohm-cm(2). Moreover, these transistors show a positive temperature coefficient in the on-resistance and a negative temperature coefficient in the current gain, which enable easy paralleling of the devices. In addition, RF BJTs were designed, fabricated and tested for operation at UHF frequencies. Three cells were measured in common emitter (CE) mode with a collector supply voltage of 80 V in class AB at 425 MHz. A 100 mus pulse width with 10% duty cycle was used. A maximum output power of 150 W was achieved. This represents the first practical demonstration of a SiC RF BJT.