The problem of the VOH(min) of a TTL IC being too low to drive a CMOS circuit and meet the CMOS requirement of VIH(min) is usually easily overcome by:

• adding a fixed voltage-divider bias resistive network at the output of the TTL device
• avoiding this condition and only using TTL to drive TTL
• adding an external pull-down resistor to ground
• adding an external pull-up resistor to VCC